_axes.py

from __future__ import (absolute_import, division, print_function,
                        unicode_literals)

import six
from six.moves import reduce, xrange, zip

import math
import warnings
import itertools

import numpy as np
from numpy import ma

import matplotlib
rcParams = matplotlib.rcParams

import matplotlib.cbook as cbook
from matplotlib.cbook import _string_to_bool, mplDeprecation
import matplotlib.collections as mcoll
import matplotlib.colors as mcolors
import matplotlib.contour as mcontour
import matplotlib.dates as _  # <-registers a date unit converter
from matplotlib import docstring
import matplotlib.image as mimage
import matplotlib.legend as mlegend
import matplotlib.lines as mlines
import matplotlib.markers as mmarkers
import matplotlib.mlab as mlab
import matplotlib.path as mpath
import matplotlib.patches as mpatches
import matplotlib.quiver as mquiver
import matplotlib.stackplot as mstack
import matplotlib.streamplot as mstream
import matplotlib.table as mtable
import matplotlib.text as mtext
import matplotlib.ticker as mticker
import matplotlib.transforms as mtransforms
import matplotlib.tri as mtri
import matplotlib.transforms as mtrans
from matplotlib.container import BarContainer, ErrorbarContainer, StemContainer
from matplotlib.axes._base import _AxesBase
from matplotlib.axes._base import _process_plot_format

iterable = cbook.iterable
is_string_like = cbook.is_string_like
is_sequence_of_strings = cbook.is_sequence_of_strings


# The axes module contains all the wrappers to plotting functions.
# All the other methods should go in the _AxesBase class.

class Axes(_AxesBase):
    """
    The :class:`Axes` contains most of the figure elements:
    :class:`~matplotlib.axis.Axis`, :class:`~matplotlib.axis.Tick`,
    :class:`~matplotlib.lines.Line2D`, :class:`~matplotlib.text.Text`,
    :class:`~matplotlib.patches.Polygon`, etc., and sets the
    coordinate system.

    The :class:`Axes` instance supports callbacks through a callbacks
    attribute which is a :class:`~matplotlib.cbook.CallbackRegistry`
    instance.  The events you can connect to are 'xlim_changed' and
    'ylim_changed' and the callback will be called with func(*ax*)
    where *ax* is the :class:`Axes` instance.
    """
    ### Labelling, legend and texts

    def get_title(self, loc="center"):
        """Get an axes title.

        Get one of the three available axes titles. The available titles
        are positioned above the axes in the center, flush with the left
        edge, and flush with the right edge.

        Parameters
        ----------
        loc : {'center', 'left', 'right'}, str, optional
            Which title to get, defaults to 'center'

        Returns
        -------
        title: str
            The title text string.

        """
        try:
            title = {'left': self._left_title,
                     'center': self.title,
                     'right': self._right_title}[loc.lower()]
        except KeyError:
            raise ValueError("'%s' is not a valid location" % loc)
        return title.get_text()

    @docstring.dedent_interpd
    def set_title(self, label, fontdict=None, loc="center", **kwargs):
        """
        Set a title for the axes.

        Set one of the three available axes titles. The available titles
        are positioned above the axes in the center, flush with the left
        edge, and flush with the right edge.

        Parameters
        ----------
        label : str
            Text to use for the title

        fontdict : dict
            A dictionary controlling the appearance of the title text,
            the default `fontdict` is::

               {'fontsize': rcParams['axes.titlesize'],
                'fontweight' : rcParams['axes.titleweight'],
                'verticalalignment': 'baseline',
                'horizontalalignment': loc}

        loc : {'center', 'left', 'right'}, str, optional
            Which title to set, defaults to 'center'

        Returns
        -------
        text : :class:`~matplotlib.text.Text`
            The matplotlib text instance representing the title

        Other parameters
        ----------------
        kwargs : text properties
            Other keyword arguments are text properties, see
            :class:`~matplotlib.text.Text` for a list of valid text
            properties.
        """
        try:
            title = {'left': self._left_title,
                     'center': self.title,
                     'right': self._right_title}[loc.lower()]
        except KeyError:
            raise ValueError("'%s' is not a valid location" % loc)
        default = {
            'fontsize': rcParams['axes.titlesize'],
            'fontweight': rcParams['axes.titleweight'],
            'verticalalignment': 'baseline',
            'horizontalalignment': loc.lower()}
        title.set_text(label)
        title.update(default)
        if fontdict is not None:
            title.update(fontdict)
        title.update(kwargs)
        return title

    def get_xlabel(self):
        """
        Get the xlabel text string.
        """
        label = self.xaxis.get_label()
        return label.get_text()

    @docstring.dedent_interpd
    def set_xlabel(self, xlabel, fontdict=None, labelpad=None, **kwargs):
        """
        Set the label for the xaxis.

        Parameters
        ----------
        xlabel : string
            x label

        labelpad : scalar, optional, default: None
            spacing in points between the label and the x-axis

        Other parameters
        ----------------
        kwargs : `~matplotlib.text.Text` properties

        See also
        --------
        text : for information on how override and the optional args work
        """
        if labelpad is not None:
            self.xaxis.labelpad = labelpad
        return self.xaxis.set_label_text(xlabel, fontdict, **kwargs)

    def get_ylabel(self):
        """
        Get the ylabel text string.
        """
        label = self.yaxis.get_label()
        return label.get_text()

    @docstring.dedent_interpd
    def set_ylabel(self, ylabel, fontdict=None, labelpad=None, **kwargs):
        """
        Set the label for the yaxis

        Parameters
        ----------
        ylabel : string
            y label

        labelpad : scalar, optional, default: None
            spacing in points between the label and the x-axis

        Other parameters
        ----------------
        kwargs : `~matplotlib.text.Text` properties

        See also
        --------
        text : for information on how override and the optional args work

        """
        if labelpad is not None:
            self.yaxis.labelpad = labelpad
        return self.yaxis.set_label_text(ylabel, fontdict, **kwargs)

    def _get_legend_handles(self, legend_handler_map=None):
        """
        Return a generator of artists that can be used as handles in
        a legend.

        """
        handles_original = (self.lines + self.patches +
                            self.collections + self.containers)
        handler_map = mlegend.Legend.get_default_handler_map()

        if legend_handler_map is not None:
            handler_map = handler_map.copy()
            handler_map.update(legend_handler_map)

        has_handler = mlegend.Legend.get_legend_handler

        for handle in handles_original:
            label = handle.get_label()
            if label != '_nolegend_' and has_handler(handler_map, handle):
                yield handle

    def get_legend_handles_labels(self, legend_handler_map=None):
        """
        Return handles and labels for legend

        ``ax.legend()`` is equivalent to ::

          h, l = ax.get_legend_handles_labels()
          ax.legend(h, l)

        """
        handles = []
        labels = []
        for handle in self._get_legend_handles(legend_handler_map):
            label = handle.get_label()
            if label and not label.startswith('_'):
                handles.append(handle)
                labels.append(label)

        return handles, labels

    def legend(self, *args, **kwargs):
        """
        Places a legend on the axes.

        To make a legend for lines which already exist on the axes
        (via plot for instance), simply call this function with an iterable
        of strings, one for each legend item. For example::

            ax.plot([1, 2, 3])
            ax.legend(['A simple line'])

        However, in order to keep the "label" and the legend element
        instance together, it is preferable to specify the label either at
        artist creation, or by calling the
        :meth:`~matplotlib.artist.Artist.set_label` method on the artist::

            line, = ax.plot([1, 2, 3], label='Inline label')
            # Overwrite the label by calling the method.
            line.set_label('Label via method')
            ax.legend()

        Specific lines can be excluded from the automatic legend element
        selection by defining a label starting with an underscore.
        This is default for all artists, so calling :meth:`legend` without
        any arguments and without setting the labels manually will result in
        no legend being drawn.

        For full control of which artists have a legend entry, it is possible
        to pass an iterable of legend artists followed by an iterable of
        legend labels respectively::

           legend((line1, line2, line3), ('label1', 'label2', 'label3'))

        Parameters
        ----------
        loc : int or string or pair of floats, default: 0
            The location of the legend. Possible codes are:

                ===============   =============
                Location String   Location Code
                ===============   =============
                'best'            0
                'upper right'     1
                'upper left'      2
                'lower left'      3
                'lower right'     4
                'right'           5
                'center left'     6
                'center right'    7
                'lower center'    8
                'upper center'    9
                'center'          10
                ===============   =============


            Alternatively can be a 2-tuple giving ``x, y`` of the lower-left
            corner of the legend in axes coordinates (in which case
            ``bbox_to_anchor`` will be ignored).

        bbox_to_anchor : :class:`matplotlib.transforms.BboxBase` instance \
                         or tuple of floats
            Specify any arbitrary location for the legend in `bbox_transform`
            coordinates (default Axes coordinates).

            For example, to put the legend's upper right hand corner in the
            center of the axes the following keywords can be used::

               loc='upper right', bbox_to_anchor=(0.5, 0.5)

        ncol : integer
            The number of columns that the legend has. Default is 1.

        prop : None or :class:`matplotlib.font_manager.FontProperties` or dict
            The font properties of the legend. If None (default), the current
            :data:`matplotlib.rcParams` will be used.

        fontsize : int or float or {'xx-small', 'x-small', 'small', 'medium',\
                   'large', 'x-large', 'xx-large'}
            Controls the font size of the legend. If the value is numeric the
            size will be the absolute font size in points. String values are
            relative to the current default font size. This argument is only
            used if `prop` is not specified.

        numpoints : None or int
            The number of marker points in the legend when creating a legend
            entry for a line/:class:`matplotlib.lines.Line2D`.
            Default is ``None`` which will take the value from the
            ``legend.numpoints`` :data:`rcParam<matplotlib.rcParams>`.

        scatterpoints : None or int
            The number of marker points in the legend when creating a legend
            entry for a scatter plot/
            :class:`matplotlib.collections.PathCollection`.
            Default is ``None`` which will take the value from the
            ``legend.scatterpoints`` :data:`rcParam<matplotlib.rcParams>`.

        scatteryoffsets : iterable of floats
            The vertical offset (relative to the font size) for the markers
            created for a scatter plot legend entry. 0.0 is at the base the
            legend text, and 1.0 is at the top. To draw all markers at the
            same height, set to ``[0.5]``. Default ``[0.375, 0.5, 0.3125]``.

        markerscale : None or int or float
            The relative size of legend markers compared with the originally
            drawn ones. Default is ``None`` which will take the value from
            the ``legend.markerscale`` :data:`rcParam <matplotlib.rcParams>`.

        *markerfirst*: [ *True* | *False* ]
            if *True*, legend marker is placed to the left of the legend label
            if *False*, legend marker is placed to the right of the legend
            label

        frameon : None or bool
            Control whether a frame should be drawn around the legend.
            Default is ``None`` which will take the value from the
            ``legend.frameon`` :data:`rcParam<matplotlib.rcParams>`.

        fancybox : None or bool
            Control whether round edges should be enabled around
            the :class:`~matplotlib.patches.FancyBboxPatch` which
            makes up the legend's background.
            Default is ``None`` which will take the value from the
            ``legend.fancybox`` :data:`rcParam<matplotlib.rcParams>`.

        shadow : None or bool
            Control whether to draw a shadow behind the legend.
            Default is ``None`` which will take the value from the
            ``legend.shadow`` :data:`rcParam<matplotlib.rcParams>`.

        framealpha : None or float
            Control the alpha transparency of the legend's frame.
            Default is ``None`` which will take the value from the
            ``legend.framealpha`` :data:`rcParam<matplotlib.rcParams>`.

        mode : {"expand", None}
            If `mode` is set to ``"expand"`` the legend will be horizontally
            expanded to fill the axes area (or `bbox_to_anchor` if defines
            the legend's size).

        bbox_transform : None or :class:`matplotlib.transforms.Transform`
            The transform for the bounding box (`bbox_to_anchor`). For a value
            of ``None`` (default) the Axes'
            :data:`~matplotlib.axes.Axes.transAxes` transform will be used.

        title : str or None
            The legend's title. Default is no title (``None``).

        borderpad : float or None
            The fractional whitespace inside the legend border.
            Measured in font-size units.
            Default is ``None`` which will take the value from the
            ``legend.borderpad`` :data:`rcParam<matplotlib.rcParams>`.

        labelspacing : float or None
            The vertical space between the legend entries.
            Measured in font-size units.
            Default is ``None`` which will take the value from the
            ``legend.labelspacing`` :data:`rcParam<matplotlib.rcParams>`.

        handlelength : float or None
            The length of the legend handles.
            Measured in font-size units.
            Default is ``None`` which will take the value from the
            ``legend.handlelength`` :data:`rcParam<matplotlib.rcParams>`.

        handletextpad : float or None
            The pad between the legend handle and text.
            Measured in font-size units.
            Default is ``None`` which will take the value from the
            ``legend.handletextpad`` :data:`rcParam<matplotlib.rcParams>`.

        borderaxespad : float or None
            The pad between the axes and legend border.
            Measured in font-size units.
            Default is ``None`` which will take the value from the
            ``legend.borderaxespad`` :data:`rcParam<matplotlib.rcParams>`.

        columnspacing : float or None
            The spacing between columns.
            Measured in font-size units.
            Default is ``None`` which will take the value from the
            ``legend.columnspacing`` :data:`rcParam<matplotlib.rcParams>`.

        handler_map : dict or None
            The custom dictionary mapping instances or types to a legend
            handler. This `handler_map` updates the default handler map
            found at :func:`matplotlib.legend.Legend.get_legend_handler_map`.

        Notes
        -----

        Not all kinds of artist are supported by the legend command.
        See :ref:`plotting-guide-legend` for details.

        Examples
        --------

        .. plot:: mpl_examples/api/legend_demo.py

        """
        handlers = kwargs.get('handler_map', {}) or {}

        # Support handles and labels being passed as keywords.
        handles = kwargs.pop('handles', None)
        labels = kwargs.pop('labels', None)

        if handles is not None and labels is None:
            labels = [handle.get_label() for handle in handles]
            for label, handle in zip(labels[:], handles[:]):
                if label.startswith('_'):
                    warnings.warn('The handle {!r} has a label of {!r} which '
                                  'cannot be automatically added to the '
                                  'legend.'.format(handle, label))
                    labels.remove(label)
                    handles.remove(handle)

        elif labels is not None and handles is None:
            # Get as many handles as there are labels.
            handles = [handle for handle, _
                       in zip(self._get_legend_handles(handlers), labels)]

        # No arguments - automatically detect labels and handles.
        elif len(args) == 0:
            handles, labels = self.get_legend_handles_labels(handlers)
            if not handles:
                warnings.warn("No labelled objects found. "
                              "Use label='...' kwarg on individual plots.")
                return None

        # One argument. User defined labels - automatic handle detection.
        elif len(args) == 1:
            labels, = args
            # Get as many handles as there are labels.
            handles = [handle for handle, _
                       in zip(self._get_legend_handles(handlers), labels)]

        # Two arguments. Either:
        #   * user defined handles and labels
        #   * user defined labels and location (deprecated)
        elif len(args) == 2:
            if is_string_like(args[1]) or isinstance(args[1], int):
                cbook.warn_deprecated('1.4', 'The "loc" positional argument '
                                      'to legend is deprecated. Please use '
                                      'the "loc" keyword instead.')
                labels, loc = args
                handles = [handle for handle, _
                           in zip(self._get_legend_handles(handlers), labels)]
                kwargs['loc'] = loc
            else:
                handles, labels = args

        # Three arguments. User defined handles, labels and
        # location (deprecated).
        elif len(args) == 3:
            cbook.warn_deprecated('1.4', 'The "loc" positional argument '
                                         'to legend is deprecated. Please '
                                         'use the "loc" keyword instead.')
            handles, labels, loc = args
            kwargs['loc'] = loc

        else:
            raise TypeError('Invalid arguments to legend.')

        self.legend_ = mlegend.Legend(self, handles, labels, **kwargs)
        self.legend_._remove_method = lambda h: setattr(self, 'legend_', None)
        return self.legend_

    def text(self, x, y, s, fontdict=None,
             withdash=False, **kwargs):
        """
        Add text to the axes.

        Add text in string `s` to axis at location `x`, `y`, data
        coordinates.

        Parameters
        ----------
        x, y : scalars
            data coordinates

        s : string
            text

        fontdict : dictionary, optional, default: None
            A dictionary to override the default text properties. If fontdict
            is None, the defaults are determined by your rc parameters.

        withdash : boolean, optional, default: False
            Creates a `~matplotlib.text.TextWithDash` instance instead of a
            `~matplotlib.text.Text` instance.

        Other parameters
        ----------------
        kwargs : `~matplotlib.text.Text` properties.
            Other miscellaneous text parameters.

        Examples
        --------
        Individual keyword arguments can be used to override any given
        parameter::

            >>> text(x, y, s, fontsize=12)

        The default transform specifies that text is in data coords,
        alternatively, you can specify text in axis coords (0,0 is
        lower-left and 1,1 is upper-right).  The example below places
        text in the center of the axes::

            >>> text(0.5, 0.5,'matplotlib', horizontalalignment='center',
            ...      verticalalignment='center',
            ...      transform=ax.transAxes)

        You can put a rectangular box around the text instance (e.g., to
        set a background color) by using the keyword `bbox`.  `bbox` is
        a dictionary of `~matplotlib.patches.Rectangle`
        properties.  For example::

            >>> text(x, y, s, bbox=dict(facecolor='red', alpha=0.5))
        """
        default = {
            'verticalalignment': 'baseline',
            'horizontalalignment': 'left',
            'transform': self.transData,
            'clip_on': False}

        # At some point if we feel confident that TextWithDash
        # is robust as a drop-in replacement for Text and that
        # the performance impact of the heavier-weight class
        # isn't too significant, it may make sense to eliminate
        # the withdash kwarg and simply delegate whether there's
        # a dash to TextWithDash and dashlength.
        if withdash:
            t = mtext.TextWithDash(
                x=x, y=y, text=s)
        else:
            t = mtext.Text(
                x=x, y=y, text=s)
        self._set_artist_props(t)

        t.update(default)
        if fontdict is not None:
            t.update(fontdict)
        t.update(kwargs)
        self.texts.append(t)
        t._remove_method = lambda h: self.texts.remove(h)

        t.set_clip_path(self.patch)
        return t

    @docstring.dedent_interpd
    def annotate(self, *args, **kwargs):
        """
        Create an annotation: a piece of text referring to a data
        point.

        Parameters
        ----------
        s : string
            label

        xy : (x, y)
            position of element to annotate

        xytext : (x, y) , optional, default: None
            position of the label `s`

        xycoords : string, optional, default: "data"
            string that indicates what type of coordinates `xy` is. Examples:
            "figure points", "figure pixels", "figure fraction", "axes
            points", .... See `matplotlib.text.Annotation` for more details.

        textcoords : string, optional
            string that indicates what type of coordinates `text` is. Examples:
            "figure points", "figure pixels", "figure fraction", "axes
            points", .... See `matplotlib.text.Annotation` for more details.
            Default is None.

        arrowprops : `matplotlib.lines.Line2D` properties, optional
            Dictionary of line properties for the arrow that connects
            the annotation to the point. If the dictionnary has a key
            `arrowstyle`, a `~matplotlib.patches.FancyArrowPatch`
            instance is created and drawn.  See
            `matplotlib.text.Annotation` for more details on valid
            options. Default is None.

        Returns
        -------
        a : `~matplotlib.text.Annotation`


        Notes
        -----

        %(Annotation)s

        Examples
        --------

        .. plot:: mpl_examples/pylab_examples/annotation_demo2.py
        """
        a = mtext.Annotation(*args, **kwargs)
        a.set_transform(mtransforms.IdentityTransform())
        self._set_artist_props(a)
        if 'clip_on' in kwargs:
            a.set_clip_path(self.patch)
        self.texts.append(a)
        a._remove_method = lambda h: self.texts.remove(h)
        return a

    #### Lines and spans

    @docstring.dedent_interpd
    def axhline(self, y=0, xmin=0, xmax=1, **kwargs):
        """
        Add a horizontal line across the axis.

        Parameters
        ----------
        y : scalar, optional, default: 0
            y position in data coordinates of the horizontal line.

        xmin : scalar, optional, default: 0
            Should be between 0 and 1, 0 being the far left of the plot, 1 the
            far right of the plot.

        xmax : scalar, optional, default: 1
            Should be between 0 and 1, 0 being the far left of the plot, 1 the
            far right of the plot.

        Returns
        -------
        `~matplotlib.lines.Line2D`

        Notes
        -----
        kwargs are the same as kwargs to plot, and can be
        used to control the line properties.  e.g.,

        Examples
        --------

        * draw a thick red hline at 'y' = 0 that spans the xrange::

            >>> axhline(linewidth=4, color='r')

        * draw a default hline at 'y' = 1 that spans the xrange::

            >>> axhline(y=1)

        * draw a default hline at 'y' = .5 that spans the the middle half of
          the xrange::

            >>> axhline(y=.5, xmin=0.25, xmax=0.75)

        Valid kwargs are :class:`~matplotlib.lines.Line2D` properties,
        with the exception of 'transform':

        %(Line2D)s

        See also
        --------
        axhspan : for example plot and source code
        """

        if "transform" in kwargs:
            raise ValueError(
                "'transform' is not allowed as a kwarg;"
                + "axhline generates its own transform.")
        ymin, ymax = self.get_ybound()

        # We need to strip away the units for comparison with
        # non-unitized bounds
        self._process_unit_info(ydata=y, kwargs=kwargs)
        yy = self.convert_yunits(y)
        scaley = (yy < ymin) or (yy > ymax)

        trans = self.get_yaxis_transform(which='grid')
        l = mlines.Line2D([xmin, xmax], [y, y], transform=trans, **kwargs)
        self.add_line(l)
        self.autoscale_view(scalex=False, scaley=scaley)
        return l

    @docstring.dedent_interpd
    def axvline(self, x=0, ymin=0, ymax=1, **kwargs):
        """
        Add a vertical line across the axes.

        Parameters
        ----------
        x : scalar, optional, default: 0
            x position in data coordinates of the vertical line.

        ymin : scalar, optional, default: 0
            Should be between 0 and 1, 0 being the far left of the plot, 1 the
            far right of the plot.

        ymax : scalar, optional, default: 1
            Should be between 0 and 1, 0 being the far left of the plot, 1 the
            far right of the plot.

        Returns
        -------
        `~matplotlib.lines.Line2D`


        Examples
        ---------
        * draw a thick red vline at *x* = 0 that spans the yrange::

            >>> axvline(linewidth=4, color='r')

        * draw a default vline at *x* = 1 that spans the yrange::

            >>> axvline(x=1)

        * draw a default vline at *x* = .5 that spans the the middle half of
          the yrange::

            >>> axvline(x=.5, ymin=0.25, ymax=0.75)

        Valid kwargs are :class:`~matplotlib.lines.Line2D` properties,
        with the exception of 'transform':

        %(Line2D)s

        See also
        --------
        axhspan : for example plot and source code
        """

        if "transform" in kwargs:
            raise ValueError(
                "'transform' is not allowed as a kwarg;"
                + "axvline generates its own transform.")
        xmin, xmax = self.get_xbound()

        # We need to strip away the units for comparison with
        # non-unitized bounds
        self._process_unit_info(xdata=x, kwargs=kwargs)
        xx = self.convert_xunits(x)
        scalex = (xx < xmin) or (xx > xmax)

        trans = self.get_xaxis_transform(which='grid')
        l = mlines.Line2D([x, x], [ymin, ymax], transform=trans, **kwargs)
        self.add_line(l)
        self.autoscale_view(scalex=scalex, scaley=False)
        return l

    @docstring.dedent_interpd
    def axhspan(self, ymin, ymax, xmin=0, xmax=1, **kwargs):
        """
        Add a horizontal span (rectangle) across the axis.

        Call signature::

          axhspan(ymin, ymax, xmin=0, xmax=1, **kwargs)

        *y* coords are in data units and *x* coords are in axes (relative
        0-1) units.

        Draw a horizontal span (rectangle) from *ymin* to *ymax*.
        With the default values of *xmin* = 0 and *xmax* = 1, this
        always spans the xrange, regardless of the xlim settings, even
        if you change them, e.g., with the :meth:`set_xlim` command.
        That is, the horizontal extent is in axes coords: 0=left,
        0.5=middle, 1.0=right but the *y* location is in data
        coordinates.

        Return value is a :class:`matplotlib.patches.Polygon`
        instance.

       Examples:

        * draw a gray rectangle from *y* = 0.25-0.75 that spans the
          horizontal extent of the axes::

            >>> axhspan(0.25, 0.75, facecolor='0.5', alpha=0.5)

        Valid kwargs are :class:`~matplotlib.patches.Polygon` properties:

        %(Polygon)s

        **Example:**

        .. plot:: mpl_examples/pylab_examples/axhspan_demo.py

        """
        trans = self.get_yaxis_transform(which='grid')

        # process the unit information
        self._process_unit_info([xmin, xmax], [ymin, ymax], kwargs=kwargs)

        # first we need to strip away the units
        xmin, xmax = self.convert_xunits([xmin, xmax])
        ymin, ymax = self.convert_yunits([ymin, ymax])

        verts = (xmin, ymin), (xmin, ymax), (xmax, ymax), (xmax, ymin)
        p = mpatches.Polygon(verts, **kwargs)
        p.set_transform(trans)
        self.add_patch(p)
        self.autoscale_view(scalex=False)
        return p

    @docstring.dedent_interpd
    def axvspan(self, xmin, xmax, ymin=0, ymax=1, **kwargs):
        """
        Add a vertical span (rectangle) across the axes.

        Call signature::

          axvspan(xmin, xmax, ymin=0, ymax=1, **kwargs)

        *x* coords are in data units and *y* coords are in axes (relative
        0-1) units.

        Draw a vertical span (rectangle) from *xmin* to *xmax*.  With
        the default values of *ymin* = 0 and *ymax* = 1, this always
        spans the yrange, regardless of the ylim settings, even if you
        change them, e.g., with the :meth:`set_ylim` command.  That is,
        the vertical extent is in axes coords: 0=bottom, 0.5=middle,
        1.0=top but the *y* location is in data coordinates.

        Return value is the :class:`matplotlib.patches.Polygon`
        instance.

        Examples:

        * draw a vertical green translucent rectangle from x=1.25 to 1.55 that
          spans the yrange of the axes::

            >>> axvspan(1.25, 1.55, facecolor='g', alpha=0.5)

        Valid kwargs are :class:`~matplotlib.patches.Polygon`
        properties:

        %(Polygon)s

        .. seealso::

            :meth:`axhspan`
                for example plot and source code
        """
        trans = self.get_xaxis_transform(which='grid')

        # process the unit information
        self._process_unit_info([xmin, xmax], [ymin, ymax], kwargs=kwargs)

        # first we need to strip away the units
        xmin, xmax = self.convert_xunits([xmin, xmax])
        ymin, ymax = self.convert_yunits([ymin, ymax])

        verts = [(xmin, ymin), (xmin, ymax), (xmax, ymax), (xmax, ymin)]
        p = mpatches.Polygon(verts, **kwargs)
        p.set_transform(trans)
        self.add_patch(p)
        self.autoscale_view(scaley=False)
        return p

    @docstring.dedent
    def hlines(self, y, xmin, xmax, colors='k', linestyles='solid',
               label='', **kwargs):
        """
        Plot horizontal lines at each `y` from `xmin` to `xmax`.

        Parameters
        ----------
        y : scalar or sequence of scalar
            y-indexes where to plot the lines.

        xmin, xmax : scalar or 1D array_like
            Respective beginning and end of each line. If scalars are
            provided, all lines will have same length.

        colors : array_like of colors, optional, default: 'k'

        linestyles : ['solid' | 'dashed' | 'dashdot' | 'dotted'], optional

        label : string, optional, default: ''

        Returns
        -------
        lines : `~matplotlib.collections.LineCollection`

        Other parameters
        ----------------
        kwargs :  `~matplotlib.collections.LineCollection` properties.

        See also
        --------
        vlines : vertical lines

        Examples
        --------
        .. plot:: mpl_examples/pylab_examples/vline_hline_demo.py

        """

        # We do the conversion first since not all unitized data is uniform
        # process the unit information
        self._process_unit_info([xmin, xmax], y, kwargs=kwargs)
        y = self.convert_yunits(y)
        xmin = self.convert_xunits(xmin)
        xmax = self.convert_xunits(xmax)

        if not iterable(y):
            y = [y]
        if not iterable(xmin):
            xmin = [xmin]
        if not iterable(xmax):
            xmax = [xmax]

        y = np.ravel(y)

        xmin = np.resize(xmin, y.shape)
        xmax = np.resize(xmax, y.shape)

        verts = [((thisxmin, thisy), (thisxmax, thisy))
                 for thisxmin, thisxmax, thisy in zip(xmin, xmax, y)]
        coll = mcoll.LineCollection(verts, colors=colors,
                                    linestyles=linestyles, label=label)
        self.add_collection(coll, autolim=False)
        coll.update(kwargs)

        if len(y) > 0:
            minx = min(xmin.min(), xmax.min())
            maxx = max(xmin.max(), xmax.max())
            miny = y.min()
            maxy = y.max()

            corners = (minx, miny), (maxx, maxy)

            self.update_datalim(corners)
            self.autoscale_view()

        return coll

    @docstring.dedent_interpd
    def vlines(self, x, ymin, ymax, colors='k', linestyles='solid',
               label='', **kwargs):
        """
        Plot vertical lines.

        Plot vertical lines at each `x` from `ymin` to `ymax`.

        Parameters
        ----------
        x : scalar or 1D array_like
            x-indexes where to plot the lines.

        ymin, ymax : scalar or 1D array_like
            Respective beginning and end of each line. If scalars are
            provided, all lines will have same length.

        colors : array_like of colors, optional, default: 'k'

        linestyles : ['solid' | 'dashed' | 'dashdot' | 'dotted'], optional

        label : string, optional, default: ''

        Returns
        -------
        lines : `~matplotlib.collections.LineCollection`

        Other parameters
        ----------------
        kwargs : `~matplotlib.collections.LineCollection` properties.

        See also
        --------
        hlines : horizontal lines

        Examples
        ---------
        .. plot:: mpl_examples/pylab_examples/vline_hline_demo.py

        """

        self._process_unit_info(xdata=x, ydata=[ymin, ymax], kwargs=kwargs)

        # We do the conversion first since not all unitized data is uniform
        x = self.convert_xunits(x)
        ymin = self.convert_yunits(ymin)
        ymax = self.convert_yunits(ymax)

        if not iterable(x):
            x = [x]
        if not iterable(ymin):
            ymin = [ymin]
        if not iterable(ymax):
            ymax = [ymax]

        x = np.ravel(x)
        ymin = np.resize(ymin, x.shape)
        ymax = np.resize(ymax, x.shape)

        verts = [((thisx, thisymin), (thisx, thisymax))
                 for thisx, thisymin, thisymax in zip(x, ymin, ymax)]
        #print 'creating line collection'
        coll = mcoll.LineCollection(verts, colors=colors,
                                    linestyles=linestyles, label=label)
        self.add_collection(coll, autolim=False)
        coll.update(kwargs)

        if len(x) > 0:
            minx = min(x)
            maxx = max(x)

            miny = min(min(ymin), min(ymax))
            maxy = max(max(ymin), max(ymax))

            corners = (minx, miny), (maxx, maxy)
            self.update_datalim(corners)
            self.autoscale_view()

        return coll

    @docstring.dedent_interpd
    def eventplot(self, positions, orientation='horizontal', lineoffsets=1,
                  linelengths=1, linewidths=None, colors=None,
                  linestyles='solid', **kwargs):
        """
        Plot identical parallel lines at specific positions.

        Call signature::

          eventplot(positions, orientation='horizontal', lineoffsets=0,
                    linelengths=1, linewidths=None, color =None,
                    linestyles='solid'

        Plot parallel lines at the given positions.  positions should be a 1D
        or 2D array-like object, with each row corresponding to a row or column
        of lines.

        This type of plot is commonly used in neuroscience for representing
        neural events, where it is commonly called a spike raster, dot raster,
        or raster plot.

        However, it is useful in any situation where you wish to show the
        timing or position of multiple sets of discrete events, such as the
        arrival times of people to a business on each day of the month or the
        date of hurricanes each year of the last century.

        *orientation* : [ 'horizonal' | 'vertical' ]
          'horizonal' : the lines will be vertical and arranged in rows
          "vertical' : lines will be horizontal and arranged in columns

        *lineoffsets* :
          A float or array-like containing floats.

        *linelengths* :
          A float or array-like containing floats.

        *linewidths* :
          A float or array-like containing floats.

        *colors*
          must be a sequence of RGBA tuples (e.g., arbitrary color
          strings, etc, not allowed) or a list of such sequences

        *linestyles* :
          [ 'solid' | 'dashed' | 'dashdot' | 'dotted' ] or an array of these
          values

        For linelengths, linewidths, colors, and linestyles, if only a single
        value is given, that value is applied to all lines.  If an array-like
        is given, it must have the same length as positions, and each value
        will be applied to the corresponding row or column in positions.

        Returns a list of :class:`matplotlib.collections.EventCollection`
        objects that were added.

        kwargs are :class:`~matplotlib.collections.LineCollection` properties:

        %(LineCollection)s

        **Example:**

        .. plot:: mpl_examples/pylab_examples/eventplot_demo.py
        """
        self._process_unit_info(xdata=positions,
                                ydata=[lineoffsets, linelengths],
                                kwargs=kwargs)

        # We do the conversion first since not all unitized data is uniform
        positions = self.convert_xunits(positions)
        lineoffsets = self.convert_yunits(lineoffsets)
        linelengths = self.convert_yunits(linelengths)

        if not iterable(positions):
            positions = [positions]
        elif any(iterable(position) for position in positions):
            positions = [np.asanyarray(position) for position in positions]
        else:
            positions = [np.asanyarray(positions)]

        if len(positions) == 0:
            return []

        if not iterable(lineoffsets):
            lineoffsets = [lineoffsets]
        if not iterable(linelengths):
            linelengths = [linelengths]
        if not iterable(linewidths):
            linewidths = [linewidths]
        if not iterable(colors):
            colors = [colors]
        if hasattr(linestyles, 'lower') or not iterable(linestyles):
            linestyles = [linestyles]

        lineoffsets = np.asarray(lineoffsets)
        linelengths = np.asarray(linelengths)
        linewidths = np.asarray(linewidths)

        if len(lineoffsets) == 0:
            lineoffsets = [None]
        if len(linelengths) == 0:
            linelengths = [None]
        if len(linewidths) == 0:
            lineoffsets = [None]
        if len(linewidths) == 0:
            lineoffsets = [None]
        if len(colors) == 0:
            colors = [None]

        if len(lineoffsets) == 1 and len(positions) != 1:
            lineoffsets = np.tile(lineoffsets, len(positions))
            lineoffsets[0] = 0
            lineoffsets = np.cumsum(lineoffsets)
        if len(linelengths) == 1:
            linelengths = np.tile(linelengths, len(positions))
        if len(linewidths) == 1:
            linewidths = np.tile(linewidths, len(positions))
        if len(colors) == 1:
            colors = list(colors)
            colors = colors * len(positions)
        if len(linestyles) == 1:
            linestyles = [linestyles] * len(positions)

        if len(lineoffsets) != len(positions):
            raise ValueError('lineoffsets and positions are unequal sized '
                             'sequences')
        if len(linelengths) != len(positions):
            raise ValueError('linelengths and positions are unequal sized '
                             'sequences')
        if len(linewidths) != len(positions):
            raise ValueError('linewidths and positions are unequal sized '
                             'sequences')
        if len(colors) != len(positions):
            raise ValueError('colors and positions are unequal sized '
                             'sequences')
        if len(linestyles) != len(positions):
            raise ValueError('linestyles and positions are unequal sized '
                             'sequences')

        colls = []
        for position, lineoffset, linelength, linewidth, color, linestyle in \
            zip(positions, lineoffsets, linelengths, linewidths,
                           colors, linestyles):
            coll = mcoll.EventCollection(position,
                                         orientation=orientation,
                                         lineoffset=lineoffset,
                                         linelength=linelength,
                                         linewidth=linewidth,
                                         color=color,
                                         linestyle=linestyle)
            self.add_collection(coll, autolim=False)
            coll.update(kwargs)
            colls.append(coll)

        if len(positions) > 0:
            # try to get min/max
            min_max = [(np.min(_p), np.max(_p)) for _p in positions
                       if len(_p) > 0]
            # if we have any non-empty positions, try to autoscale
            if len(min_max) > 0:
                mins, maxes = zip(*min_max)
                minpos = np.min(mins)
                maxpos = np.max(maxes)

                minline = (lineoffsets - linelengths).min()
                maxline = (lineoffsets + linelengths).max()

                if colls[0].is_horizontal():
                    corners = (minpos, minline), (maxpos, maxline)
                else:
                    corners = (minline, minpos), (maxline, maxpos)
                self.update_datalim(corners)
                self.autoscale_view()

        return colls

    #### Basic plotting
    @docstring.dedent_interpd
    def plot(self, *args, **kwargs):
        """
        Plot lines and/or markers to the
        :class:`~matplotlib.axes.Axes`.  *args* is a variable length
        argument, allowing for multiple *x*, *y* pairs with an
        optional format string.  For example, each of the following is
        legal::

            plot(x, y)        # plot x and y using default line style and color
            plot(x, y, 'bo')  # plot x and y using blue circle markers
            plot(y)           # plot y using x as index array 0..N-1
            plot(y, 'r+')     # ditto, but with red plusses

        If *x* and/or *y* is 2-dimensional, then the corresponding columns
        will be plotted.

        An arbitrary number of *x*, *y*, *fmt* groups can be
        specified, as in::

            a.plot(x1, y1, 'g^', x2, y2, 'g-')

        Return value is a list of lines that were added.

        By default, each line is assigned a different color specified by a
        'color cycle'.  To change this behavior, you can edit the
        axes.color_cycle rcParam.

        The following format string characters are accepted to control
        the line style or marker:

        ================    ===============================
        character           description
        ================    ===============================
        ``'-'``             solid line style
        ``'--'``            dashed line style
        ``'-.'``            dash-dot line style
        ``':'``             dotted line style
        ``'.'``             point marker
        ``','``             pixel marker
        ``'o'``             circle marker
        ``'v'``             triangle_down marker
        ``'^'``             triangle_up marker
        ``'<'``             triangle_left marker
        ``'>'``             triangle_right marker
        ``'1'``             tri_down marker
        ``'2'``             tri_up marker
        ``'3'``             tri_left marker
        ``'4'``             tri_right marker
        ``'s'``             square marker
        ``'p'``             pentagon marker
        ``'*'``             star marker
        ``'h'``             hexagon1 marker
        ``'H'``             hexagon2 marker
        ``'+'``             plus marker
        ``'x'``             x marker
        ``'D'``             diamond marker
        ``'d'``             thin_diamond marker
        ``'|'``             vline marker
        ``'_'``             hline marker
        ================    ===============================


        The following color abbreviations are supported:

        ==========  ========
        character   color
        ==========  ========
        'b'         blue
        'g'         green
        'r'         red
        'c'         cyan
        'm'         magenta
        'y'         yellow
        'k'         black
        'w'         white
        ==========  ========

        In addition, you can specify colors in many weird and
        wonderful ways, including full names (``'green'``), hex
        strings (``'#008000'``), RGB or RGBA tuples (``(0,1,0,1)``) or
        grayscale intensities as a string (``'0.8'``).  Of these, the
        string specifications can be used in place of a ``fmt`` group,
        but the tuple forms can be used only as ``kwargs``.

        Line styles and colors are combined in a single format string, as in
        ``'bo'`` for blue circles.

        The *kwargs* can be used to set line properties (any property that has
        a ``set_*`` method).  You can use this to set a line label (for auto
        legends), linewidth, anitialising, marker face color, etc.  Here is an
        example::

            plot([1,2,3], [1,2,3], 'go-', label='line 1', linewidth=2)
            plot([1,2,3], [1,4,9], 'rs',  label='line 2')
            axis([0, 4, 0, 10])
            legend()

        If you make multiple lines with one plot command, the kwargs
        apply to all those lines, e.g.::

            plot(x1, y1, x2, y2, antialised=False)

        Neither line will be antialiased.

        You do not need to use format strings, which are just
        abbreviations.  All of the line properties can be controlled
        by keyword arguments.  For example, you can set the color,
        marker, linestyle, and markercolor with::

            plot(x, y, color='green', linestyle='dashed', marker='o',
                 markerfacecolor='blue', markersize=12).

        See :class:`~matplotlib.lines.Line2D` for details.

        The kwargs are :class:`~matplotlib.lines.Line2D` properties:

        %(Line2D)s

        kwargs *scalex* and *scaley*, if defined, are passed on to
        :meth:`~matplotlib.axes.Axes.autoscale_view` to determine
        whether the *x* and *y* axes are autoscaled; the default is
        *True*.
        """
        scalex = kwargs.pop('scalex', True)
        scaley = kwargs.pop('scaley', True)

        if not self._hold:
            self.cla()
        lines = []

        for line in self._get_lines(*args, **kwargs):
            self.add_line(line)
            lines.append(line)

        self.autoscale_view(scalex=scalex, scaley=scaley)
        return lines

    @docstring.dedent_interpd
    def plot_date(self, x, y, fmt='o', tz=None, xdate=True, ydate=False,
                  **kwargs):
        """
        Plot with data with dates.

        Call signature::

           plot_date(x, y, fmt='bo', tz=None, xdate=True,
                     ydate=False, **kwargs)

        Similar to the :func:`~matplotlib.pyplot.plot` command, except
        the *x* or *y* (or both) data is considered to be dates, and the
        axis is labeled accordingly.

        *x* and/or *y* can be a sequence of dates represented as float
        days since 0001-01-01 UTC.

        Keyword arguments:

          *fmt*: string
            The plot format string.

          *tz*: [ *None* | timezone string | :class:`tzinfo` instance]
            The time zone to use in labeling dates. If *None*, defaults to rc
            value.

          *xdate*: [ *True* | *False* ]
            If *True*, the *x*-axis will be labeled with dates.

          *ydate*: [ *False* | *True* ]
            If *True*, the *y*-axis will be labeled with dates.

        Note if you are using custom date tickers and formatters, it
        may be necessary to set the formatters/locators after the call
        to :meth:`plot_date` since :meth:`plot_date` will set the
        default tick locator to
        :class:`matplotlib.dates.AutoDateLocator` (if the tick
        locator is not already set to a
        :class:`matplotlib.dates.DateLocator` instance) and the
        default tick formatter to
        :class:`matplotlib.dates.AutoDateFormatter` (if the tick
        formatter is not already set to a
        :class:`matplotlib.dates.DateFormatter` instance).

        Valid kwargs are :class:`~matplotlib.lines.Line2D` properties:

        %(Line2D)s

        .. seealso::

           :mod:`~matplotlib.dates` for helper functions

           :func:`~matplotlib.dates.date2num`,
           :func:`~matplotlib.dates.num2date` and
           :func:`~matplotlib.dates.drange` for help on creating the required
           floating point dates.
        """

        if not self._hold:
            self.cla()

        ret = self.plot(x, y, fmt, **kwargs)

        if xdate:
            self.xaxis_date(tz)
        if ydate:
            self.yaxis_date(tz)

        self.autoscale_view()

        return ret

    @docstring.dedent_interpd
    def loglog(self, *args, **kwargs):
        """
        Make a plot with log scaling on both the *x* and *y* axis.

        Call signature::

          loglog(*args, **kwargs)

        :func:`~matplotlib.pyplot.loglog` supports all the keyword
        arguments of :func:`~matplotlib.pyplot.plot` and
        :meth:`matplotlib.axes.Axes.set_xscale` /
        :meth:`matplotlib.axes.Axes.set_yscale`.

        Notable keyword arguments:

          *basex*/*basey*: scalar > 1
            Base of the *x*/*y* logarithm

          *subsx*/*subsy*: [ *None* | sequence ]
            The location of the minor *x*/*y* ticks; *None* defaults
            to autosubs, which depend on the number of decades in the
            plot; see :meth:`matplotlib.axes.Axes.set_xscale` /
            :meth:`matplotlib.axes.Axes.set_yscale` for details

          *nonposx*/*nonposy*: ['mask' | 'clip' ]
            Non-positive values in *x* or *y* can be masked as
            invalid, or clipped to a very small positive number

        The remaining valid kwargs are
        :class:`~matplotlib.lines.Line2D` properties:

        %(Line2D)s

        **Example:**

        .. plot:: mpl_examples/pylab_examples/log_demo.py

        """
        if not self._hold:
            self.cla()

        dx = {'basex': kwargs.pop('basex', 10),
              'subsx': kwargs.pop('subsx', None),
              'nonposx': kwargs.pop('nonposx', 'mask'),
              }
        dy = {'basey': kwargs.pop('basey', 10),
              'subsy': kwargs.pop('subsy', None),
              'nonposy': kwargs.pop('nonposy', 'mask'),
              }

        self.set_xscale('log', **dx)
        self.set_yscale('log', **dy)

        b = self._hold
        self._hold = True  # we've already processed the hold
        l = self.plot(*args, **kwargs)
        self._hold = b  # restore the hold

        return l

    @docstring.dedent_interpd
    def semilogx(self, *args, **kwargs):
        """
        Make a plot with log scaling on the *x* axis.

        Call signature::

          semilogx(*args, **kwargs)

        :func:`semilogx` supports all the keyword arguments of
        :func:`~matplotlib.pyplot.plot` and
        :meth:`matplotlib.axes.Axes.set_xscale`.

        Notable keyword arguments:

          *basex*: scalar > 1
            Base of the *x* logarithm

          *subsx*: [ *None* | sequence ]
            The location of the minor xticks; *None* defaults to
            autosubs, which depend on the number of decades in the
            plot; see :meth:`~matplotlib.axes.Axes.set_xscale` for
            details.

          *nonposx*: [ 'mask' | 'clip' ]
            Non-positive values in *x* can be masked as
            invalid, or clipped to a very small positive number

        The remaining valid kwargs are
        :class:`~matplotlib.lines.Line2D` properties:

        %(Line2D)s

        .. seealso::

            :meth:`loglog`
                For example code and figure
        """
        if not self._hold:
            self.cla()
        d = {'basex': kwargs.pop('basex', 10),
             'subsx': kwargs.pop('subsx', None),
             'nonposx': kwargs.pop('nonposx', 'mask'),
             }

        self.set_xscale('log', **d)
        b = self._hold
        self._hold = True  # we've already processed the hold
        l = self.plot(*args, **kwargs)
        self._hold = b  # restore the hold
        return l

    @docstring.dedent_interpd
    def semilogy(self, *args, **kwargs):
        """
        Make a plot with log scaling on the *y* axis.

        call signature::

          semilogy(*args, **kwargs)

        :func:`semilogy` supports all the keyword arguments of
        :func:`~matplotlib.pylab.plot` and
        :meth:`matplotlib.axes.Axes.set_yscale`.

        Notable keyword arguments:

          *basey*: scalar > 1
            Base of the *y* logarithm

          *subsy*: [ *None* | sequence ]
            The location of the minor yticks; *None* defaults to
            autosubs, which depend on the number of decades in the
            plot; see :meth:`~matplotlib.axes.Axes.set_yscale` for
            details.

          *nonposy*: [ 'mask' | 'clip' ]
            Non-positive values in *y* can be masked as
            invalid, or clipped to a very small positive number

        The remaining valid kwargs are
        :class:`~matplotlib.lines.Line2D` properties:

        %(Line2D)s

        .. seealso::

            :meth:`loglog`
                For example code and figure
        """
        if not self._hold:
            self.cla()
        d = {'basey': kwargs.pop('basey', 10),
             'subsy': kwargs.pop('subsy', None),
             'nonposy': kwargs.pop('nonposy', 'mask'),
             }
        self.set_yscale('log', **d)
        b = self._hold
        self._hold = True  # we've already processed the hold
        l = self.plot(*args, **kwargs)
        self._hold = b  # restore the hold

        return l

    @docstring.dedent_interpd
    def acorr(self, x, **kwargs):
        """
        Plot the autocorrelation of `x`.

        Parameters
        ----------

        x : sequence of scalar

        hold : boolean, optional, default: True

        detrend : callable, optional, default: `mlab.detrend_none`
            x is detrended by the `detrend` callable. Default is no
            normalization.

        normed : boolean, optional, default: True
            if True, normalize the data by the autocorrelation at the 0-th
            lag.

        usevlines : boolean, optional, default: True
            if True, Axes.vlines is used to plot the vertical lines from the
            origin to the acorr. Otherwise, Axes.plot is used.

        maxlags : integer, optional, default: 10
            number of lags to show. If None, will return all 2 * len(x) - 1
            lags.

        Returns
        -------
        (lags, c, line, b) : where:

          - `lags` are a length 2`maxlags+1 lag vector.
          - `c` is the 2`maxlags+1 auto correlation vectorI
          - `line` is a `~matplotlib.lines.Line2D` instance returned by
            `plot`.
          - `b` is the x-axis.

        Other parameters
        -----------------
        linestyle : `~matplotlib.lines.Line2D` prop, optional, default: None
            Only used if usevlines is False.

        marker : string, optional, default: 'o'

        Notes
        -----
        The cross correlation is performed with :func:`numpy.correlate` with
        `mode` = 2.

        Examples
        --------

        `~matplotlib.pyplot.xcorr` is top graph, and
        `~matplotlib.pyplot.acorr` is bottom graph.

        .. plot:: mpl_examples/pylab_examples/xcorr_demo.py

        """
        return self.xcorr(x, x, **kwargs)

    @docstring.dedent_interpd
    def xcorr(self, x, y, normed=True, detrend=mlab.detrend_none,
              usevlines=True, maxlags=10, **kwargs):
        """
        Plot the cross correlation between *x* and *y*.

        Parameters
        ----------

        x : sequence of scalars of length n

        y : sequence of scalars of length n

        hold : boolean, optional, default: True

        detrend : callable, optional, default: `mlab.detrend_none`
            x is detrended by the `detrend` callable. Default is no
            normalization.

        normed : boolean, optional, default: True
            if True, normalize the data by the autocorrelation at the 0-th
            lag.

        usevlines : boolean, optional, default: True
            if True, Axes.vlines is used to plot the vertical lines from the
            origin to the acorr. Otherwise, Axes.plot is used.

        maxlags : integer, optional, default: 10
            number of lags to show. If None, will return all 2 * len(x) - 1
            lags.

        Returns
        -------
        (lags, c, line, b) : where:

          - `lags` are a length 2`maxlags+1 lag vector.
          - `c` is the 2`maxlags+1 auto correlation vectorI
          - `line` is a `~matplotlib.lines.Line2D` instance returned by
            `plot`.
          - `b` is the x-axis (none, if plot is used).

        Other parameters
        -----------------
        linestyle : `~matplotlib.lines.Line2D` prop, optional, default: None
            Only used if usevlines is False.

        marker : string, optional, default: 'o'

        Notes
        -----
        The cross correlation is performed with :func:`numpy.correlate` with
        `mode` = 2.
        """

        Nx = len(x)
        if Nx != len(y):
            raise ValueError('x and y must be equal length')

        x = detrend(np.asarray(x))
        y = detrend(np.asarray(y))

        c = np.correlate(x, y, mode=2)

        if normed:
            c /= np.sqrt(np.dot(x, x) * np.dot(y, y))

        if maxlags is None:
            maxlags = Nx - 1

        if maxlags >= Nx or maxlags < 1:
            raise ValueError('maglags must be None or strictly '
                             'positive < %d' % Nx)

        lags = np.arange(-maxlags, maxlags + 1)
        c = c[Nx - 1 - maxlags:Nx + maxlags]

        if usevlines:
            a = self.vlines(lags, [0], c, **kwargs)
            b = self.axhline(**kwargs)
        else:

            kwargs.setdefault('marker', 'o')
            kwargs.setdefault('linestyle', 'None')
            a, = self.plot(lags, c, **kwargs)
            b = None
        return lags, c, a, b

    #### Specialized plotting

    def step(self, x, y, *args, **kwargs):
        """
        Make a step plot.

        Call signature::

          step(x, y, *args, **kwargs)

        Additional keyword args to :func:`step` are the same as those
        for :func:`~matplotlib.pyplot.plot`.

        *x* and *y* must be 1-D sequences, and it is assumed, but not checked,
        that *x* is uniformly increasing.

        Keyword arguments:

        *where*: [ 'pre' | 'post' | 'mid'  ]
          If 'pre', the interval from x[i] to x[i+1] has level y[i+1]

          If 'post', that interval has level y[i]

          If 'mid', the jumps in *y* occur half-way between the
          *x*-values.
        """

        where = kwargs.pop('where', 'pre')
        if where not in ('pre', 'post', 'mid'):
            raise ValueError("'where' argument to step must be "
                             "'pre', 'post' or 'mid'")
        usr_linestyle = kwargs.pop('linestyle', '')
        kwargs['linestyle'] = 'steps-' + where + usr_linestyle

        return self.plot(x, y, *args, **kwargs)

    @docstring.dedent_interpd
    def bar(self, left, height, width=0.8, bottom=None, **kwargs):
        """
        Make a bar plot.

        Make a bar plot with rectangles bounded by:

          `left`, `left` + `width`, `bottom`, `bottom` + `height`
                (left, right, bottom and top edges)

        Parameters
        ----------
        left : sequence of scalars
            the x coordinates of the left sides of the bars

        height : sequence of scalars
            the heights of the bars

        width : scalar or array-like, optional, default: 0.8
            the width(s) of the bars

        bottom : scalar or array-like, optional, default: None
            the y coordinate(s) of the bars

        color : scalar or array-like, optional
            the colors of the bar faces

        edgecolor : scalar or array-like, optional
            the colors of the bar edges

        linewidth : scalar or array-like, optional, default: None
            width of bar edge(s). If None, use default
            linewidth; If 0, don't draw edges.

        xerr : scalar or array-like, optional, default: None
            if not None, will be used to generate errorbar(s) on the bar chart

        yerr : scalar or array-like, optional, default: None
            if not None, will be used to generate errorbar(s) on the bar chart

        ecolor : scalar or array-like, optional, default: None
            specifies the color of errorbar(s)

        capsize : integer, optional, default: 3
           determines the length in points of the error bar caps

        error_kw :
            dictionary of kwargs to be passed to errorbar method. *ecolor* and
            *capsize* may be specified here rather than as independent kwargs.

        align : ['edge' | 'center'], optional, default: 'edge'
            If `edge`, aligns bars by their left edges (for vertical bars) and
            by their bottom edges (for horizontal bars). If `center`, interpret
            the `left` argument as the coordinates of the centers of the bars.

        orientation : 'vertical' | 'horizontal', optional, default: 'vertical'
            The orientation of the bars.

        log : boolean, optional, default: False
            If true, sets the axis to be log scale

        Returns
        -------
        `matplotlib.patches.Rectangle` instances.

        Notes
        -----
        The optional arguments `color`, `edgecolor`, `linewidth`,
        `xerr`, and `yerr` can be either scalars or sequences of
        length equal to the number of bars.  This enables you to use
        bar as the basis for stacked bar charts, or candlestick plots.
        Detail: `xerr` and `yerr` are passed directly to
        :meth:`errorbar`, so they can also have shape 2xN for
        independent specification of lower and upper errors.

        Other optional kwargs:

        %(Rectangle)s

        See also
        --------
        barh: Plot a horizontal bar plot.

        Examples
        --------

        **Example:** A stacked bar chart.

        .. plot:: mpl_examples/pylab_examples/bar_stacked.py
        """
        if not self._hold:
            self.cla()
        color = kwargs.pop('color', None)
        edgecolor = kwargs.pop('edgecolor', None)
        linewidth = kwargs.pop('linewidth', None)

        # Because xerr and yerr will be passed to errorbar,
        # most dimension checking and processing will be left
        # to the errorbar method.
        xerr = kwargs.pop('xerr', None)
        yerr = kwargs.pop('yerr', None)
        error_kw = kwargs.pop('error_kw', dict())
        ecolor = kwargs.pop('ecolor', None)
        capsize = kwargs.pop('capsize', 3)
        error_kw.setdefault('ecolor', ecolor)
        error_kw.setdefault('capsize', capsize)

        align = kwargs.pop('align', 'edge')
        orientation = kwargs.pop('orientation', 'vertical')
        log = kwargs.pop('log', False)
        label = kwargs.pop('label', '')

        def make_iterable(x):
            if not iterable(x):
                return [x]
            else:
                return x

        # make them safe to take len() of
        _left = left
        left = make_iterable(left)
        height = make_iterable(height)
        width = make_iterable(width)
        _bottom = bottom
        bottom = make_iterable(bottom)
        linewidth = make_iterable(linewidth)

        adjust_ylim = False
        adjust_xlim = False
        if orientation == 'vertical':
            self._process_unit_info(xdata=left, ydata=height, kwargs=kwargs)
            if log:
                self.set_yscale('log', nonposy='clip')
            # size width and bottom according to length of left
            if _bottom is None:
                if self.get_yscale() == 'log':
                    adjust_ylim = True
                bottom = [0]

            nbars = len(left)
            if len(width) == 1:
                width *= nbars
            if len(bottom) == 1:
                bottom *= nbars
        elif orientation == 'horizontal':
            self._process_unit_info(xdata=width, ydata=bottom, kwargs=kwargs)
            if log:
                self.set_xscale('log', nonposx='clip')
            # size left and height according to length of bottom
            if _left is None:
                if self.get_xscale() == 'log':
                    adjust_xlim = True
                left = [0]

            nbars = len(bottom)
            if len(left) == 1:
                left *= nbars
            if len(height) == 1:
                height *= nbars
        else:
            raise ValueError('invalid orientation: %s' % orientation)

        if len(linewidth) < nbars:
            linewidth *= nbars

        if color is None:
            color = [None] * nbars
        else:
            color = list(mcolors.colorConverter.to_rgba_array(color))
            if len(color) == 0:  # until to_rgba_array is changed
                color = [[0, 0, 0, 0]]
            if len(color) < nbars:
                color *= nbars

        if edgecolor is None:
            edgecolor = [None] * nbars
        else:
            edgecolor = list(mcolors.colorConverter.to_rgba_array(edgecolor))
            if len(edgecolor) == 0:     # until to_rgba_array is changed
                edgecolor = [[0, 0, 0, 0]]
            if len(edgecolor) < nbars:
                edgecolor *= nbars

        # FIXME: convert the following to proper input validation
        # raising ValueError; don't use assert for this.
        assert len(left) == nbars, ("incompatible sizes: argument 'left' must "
                                    "be length %d or scalar" % nbars)
        assert len(height) == nbars, ("incompatible sizes: argument 'height' "
                                      "must be length %d or scalar" %
                                      nbars)
        assert len(width) == nbars, ("incompatible sizes: argument 'width' "
                                     "must be length %d or scalar" %
                                     nbars)
        assert len(bottom) == nbars, ("incompatible sizes: argument 'bottom' "
                                      "must be length %d or scalar" %
                                      nbars)

        patches = []

        # lets do some conversions now since some types cannot be
        # subtracted uniformly
        if self.xaxis is not None:
            left = self.convert_xunits(left)
            width = self.convert_xunits(width)
            if xerr is not None:
                xerr = self.convert_xunits(xerr)

        if self.yaxis is not None:
            bottom = self.convert_yunits(bottom)
            height = self.convert_yunits(height)
            if yerr is not None:
                yerr = self.convert_yunits(yerr)

        if align == 'edge':
            pass
        elif align == 'center':
            if orientation == 'vertical':
                left = [left[i] - width[i] / 2. for i in xrange(len(left))]
            elif orientation == 'horizontal':
                bottom = [bottom[i] - height[i] / 2.
                          for i in xrange(len(bottom))]

        else:
            raise ValueError('invalid alignment: %s' % align)

        args = zip(left, bottom, width, height, color, edgecolor, linewidth)
        for l, b, w, h, c, e, lw in args:
            if h < 0:
                b += h
                h = abs(h)
            if w < 0:
                l += w
                w = abs(w)
            r = mpatches.Rectangle(
                xy=(l, b), width=w, height=h,
                facecolor=c,
                edgecolor=e,
                linewidth=lw,
                label='_nolegend_'
                )
            r.update(kwargs)
            r.get_path()._interpolation_steps = 100
            #print r.get_label(), label, 'label' in kwargs
            self.add_patch(r)
            patches.append(r)

        holdstate = self._hold
        self.hold(True)  # ensure hold is on before plotting errorbars

        if xerr is not None or yerr is not None:
            if orientation == 'vertical':
                # using list comps rather than arrays to preserve unit info
                x = [l + 0.5 * w for l, w in zip(left, width)]
                y = [b + h for b, h in zip(bottom, height)]

            elif orientation == 'horizontal':
                # using list comps rather than arrays to preserve unit info
                x = [l + w for l, w in zip(left, width)]
                y = [b + 0.5 * h for b, h in zip(bottom, height)]

            if "label" not in error_kw:
                error_kw["label"] = '_nolegend_'

            errorbar = self.errorbar(x, y,
                                     yerr=yerr, xerr=xerr,
                                     fmt='none', **error_kw)
        else:
            errorbar = None

        self.hold(holdstate)  # restore previous hold state

        if adjust_xlim:
            xmin, xmax = self.dataLim.intervalx
            xmin = np.amin([w for w in width if w > 0])
            if xerr is not None:
                xmin = xmin - np.amax(xerr)
            xmin = max(xmin * 0.9, 1e-100)
            self.dataLim.intervalx = (xmin, xmax)

        if adjust_ylim:
            ymin, ymax = self.dataLim.intervaly
            ymin = np.amin([h for h in height if h > 0])
            if yerr is not None:
                ymin = ymin - np.amax(yerr)
            ymin = max(ymin * 0.9, 1e-100)
            self.dataLim.intervaly = (ymin, ymax)
        self.autoscale_view()

        bar_container = BarContainer(patches, errorbar, label=label)
        self.add_container(bar_container)

        return bar_container

    @docstring.dedent_interpd
    def barh(self, bottom, width, height=0.8, left=None, **kwargs):
        """
        Make a horizontal bar plot.

        Make a horizontal bar plot with rectangles bounded by:

          `left`, `left` + `width`, `bottom`, `bottom` + `height`
                (left, right, bottom and top edges)

        `bottom`, `width`, `height`, and `left` can be either scalars
        or sequences

        Parameters
        ----------
        bottom : scalar or array-like
            the y coordinate(s) of the bars

        width : scalar or array-like
            the width(s) of the bars

        height : sequence of scalars, optional, default: 0.8
            the heights of the bars

        left : sequence of scalars
            the x coordinates of the left sides of the bars

        Returns
        --------
        `matplotlib.patches.Rectangle` instances.

        Other parameters
        ----------------
        color : scalar or array-like, optional
            the colors of the bars

        edgecolor : scalar or array-like, optional
            the colors of the bar edges

        linewidth : scalar or array-like, optional, default: None
            width of bar edge(s). If None, use default
            linewidth; If 0, don't draw edges.

        xerr : scalar or array-like, optional, default: None
            if not None, will be used to generate errorbar(s) on the bar chart

        yerr : scalar or array-like, optional, default: None
            if not None, will be used to generate errorbar(s) on the bar chart

        ecolor : scalar or array-like, optional, default: None
            specifies the color of errorbar(s)

        capsize : integer, optional, default: 3
           determines the length in points of the error bar caps

        error_kw :
            dictionary of kwargs to be passed to errorbar method. `ecolor` and
            `capsize` may be specified here rather than as independent kwargs.

        align : ['edge' | 'center'], optional, default: 'edge'
            If `edge`, aligns bars by their left edges (for vertical bars) and
            by their bottom edges (for horizontal bars). If `center`, interpret
            the `left` argument as the coordinates of the centers of the bars.

        orientation : 'vertical' | 'horizontal', optional, default: 'vertical'
            The orientation of the bars.

        log : boolean, optional, default: False
            If true, sets the axis to be log scale

        Notes
        -----
        The optional arguments `color`, `edgecolor`, `linewidth`,
        `xerr`, and `yerr` can be either scalars or sequences of
        length equal to the number of bars.  This enables you to use
        bar as the basis for stacked bar charts, or candlestick plots.
        Detail: `xerr` and `yerr` are passed directly to
        :meth:`errorbar`, so they can also have shape 2xN for
        independent specification of lower and upper errors.

        Other optional kwargs:

        %(Rectangle)s

        See also
        --------
        bar: Plot a vertical bar plot.
        """

        patches = self.bar(left=left, height=height, width=width,
                           bottom=bottom, orientation='horizontal', **kwargs)
        return patches

    @docstring.dedent_interpd
    def broken_barh(self, xranges, yrange, **kwargs):
        """
        Plot horizontal bars.

        Call signature::

          broken_barh(self, xranges, yrange, **kwargs)

        A collection of horizontal bars spanning *yrange* with a sequence of
        *xranges*.

        Required arguments:

          =========   ==============================
          Argument    Description
          =========   ==============================
          *xranges*   sequence of (*xmin*, *xwidth*)
          *yrange*    sequence of (*ymin*, *ywidth*)
          =========   ==============================

        kwargs are
        :class:`matplotlib.collections.BrokenBarHCollection`
        properties:

        %(BrokenBarHCollection)s

        these can either be a single argument, i.e.,::

          facecolors = 'black'

        or a sequence of arguments for the various bars, i.e.,::

          facecolors = ('black', 'red', 'green')

        **Example:**

        .. plot:: mpl_examples/pylab_examples/broken_barh.py
        """
        col = mcoll.BrokenBarHCollection(xranges, yrange, **kwargs)
        self.add_collection(col, autolim=True)
        self.autoscale_view()

        return col

    def stem(self, *args, **kwargs):
        """
        Create a stem plot.

        Call signatures::

          stem(y, linefmt='b-', markerfmt='bo', basefmt='r-')
          stem(x, y, linefmt='b-', markerfmt='bo', basefmt='r-')

        A stem plot plots vertical lines (using *linefmt*) at each *x*
        location from the baseline to *y*, and places a marker there
        using *markerfmt*.  A horizontal line at 0 is is plotted using
        *basefmt*.

        If no *x* values are provided, the default is (0, 1, ..., len(y) - 1)

        Return value is a tuple (*markerline*, *stemlines*,
        *baseline*).

        .. seealso::
            This
            `document <http://www.mathworks.com/help/techdoc/ref/stem.html>`_
            for details.


        **Example:**

        .. plot:: mpl_examples/pylab_examples/stem_plot.py
        """
        remember_hold = self._hold
        if not self._hold:
            self.cla()
        self.hold(True)

        # Assume there's at least one data array
        y = np.asarray(args[0])
        args = args[1:]

        # Try a second one
        try:
            second = np.asarray(args[0], dtype=np.float)
            x, y = y, second
            args = args[1:]
        except (IndexError, ValueError):
            # The second array doesn't make sense, or it doesn't exist
            second = np.arange(len(y))
            x = second

        # Popping some defaults
        try:
            linefmt = kwargs.pop('linefmt', args[0])
        except IndexError:
            linefmt = kwargs.pop('linefmt', 'b-')
        try:
            markerfmt = kwargs.pop('markerfmt', args[1])
        except IndexError:
            markerfmt = kwargs.pop('markerfmt', 'bo')
        try:
            basefmt = kwargs.pop('basefmt', args[2])
        except IndexError:
            basefmt = kwargs.pop('basefmt', 'r-')

        bottom = kwargs.pop('bottom', None)
        label = kwargs.pop('label', None)

        markerline, = self.plot(x, y, markerfmt, label="_nolegend_")

        if bottom is None:
            bottom = 0

        stemlines = []
        for thisx, thisy in zip(x, y):
            l, = self.plot([thisx, thisx], [bottom, thisy], linefmt,
                           label="_nolegend_")
            stemlines.append(l)

        baseline, = self.plot([np.amin(x), np.amax(x)], [bottom, bottom],
                              basefmt, label="_nolegend_")

        self.hold(remember_hold)

        stem_container = StemContainer((markerline, stemlines, baseline),
                                       label=label)
        self.add_container(stem_container)

        return stem_container

    def pie(self, x, explode=None, labels=None, colors=None,
            autopct=None, pctdistance=0.6, shadow=False, labeldistance=1.1,
            startangle=None, radius=None, counterclock=True,
            wedgeprops=None, textprops=None, center=(0, 0),
            frame=False):
        r"""
        Plot a pie chart.

        Call signature::

          pie(x, explode=None, labels=None,
              colors=('b', 'g', 'r', 'c', 'm', 'y', 'k', 'w'),
              autopct=None, pctdistance=0.6, shadow=False,
              labeldistance=1.1, startangle=None, radius=None,
              counterclock=True, wedgeprops=None, textprops=None,
              center = (0, 0), frame = False )

        Make a pie chart of array *x*.  The fractional area of each
        wedge is given by x/sum(x).  If sum(x) <= 1, then the values
        of x give the fractional area directly and the array will not
        be normalized.  The wedges are plotted counterclockwise,
        by default starting from the x-axis.

        Keyword arguments:

          *explode*: [ *None* | len(x) sequence ]
            If not *None*, is a ``len(x)`` array which specifies the
            fraction of the radius with which to offset each wedge.

          *colors*: [ *None* | color sequence ]
            A sequence of matplotlib color args through which the pie chart
            will cycle.

          *labels*: [ *None* | len(x) sequence of strings ]
            A sequence of strings providing the labels for each wedge

          *autopct*: [ *None* | format string | format function ]
            If not *None*, is a string or function used to label the wedges
            with their numeric value.  The label will be placed inside the
            wedge.  If it is a format string, the label will be ``fmt%pct``.
            If it is a function, it will be called.

          *pctdistance*: scalar
            The ratio between the center of each pie slice and the
            start of the text generated by *autopct*.  Ignored if
            *autopct* is *None*; default is 0.6.

          *labeldistance*: scalar
            The radial distance at which the pie labels are drawn

          *shadow*: [ *False* | *True* ]
            Draw a shadow beneath the pie.

          *startangle*: [ *None* | Offset angle ]
            If not *None*, rotates the start of the pie chart by *angle*
            degrees counterclockwise from the x-axis.

          *radius*: [ *None* | scalar ]
          The radius of the pie, if *radius* is *None* it will be set to 1.

          *counterclock*: [ *False* | *True* ]
            Specify fractions direction, clockwise or counterclockwise.

          *wedgeprops*: [ *None* | dict of key value pairs ]
            Dict of arguments passed to the wedge objects making the pie.
            For example, you can pass in wedgeprops = { 'linewidth' : 3 }
            to set the width of the wedge border lines equal to 3.
            For more details, look at the doc/arguments of the wedge object.
            By default `clip_on=False`.

          *textprops*: [ *None* | dict of key value pairs ]
            Dict of arguments to pass to the text objects.

          *center*: [ (0,0) | sequence of 2 scalars ]
          Center position of the chart.

          *frame*: [ *False* | *True* ]
            Plot axes frame with the chart.

        The pie chart will probably look best if the figure and axes are
        square, or the Axes aspect is equal.  e.g.::

          figure(figsize=(8,8))
          ax = axes([0.1, 0.1, 0.8, 0.8])

        or::

          axes(aspect=1)

        Return value:
          If *autopct* is *None*, return the tuple (*patches*, *texts*):

            - *patches* is a sequence of
              :class:`matplotlib.patches.Wedge` instances

            - *texts* is a list of the label
              :class:`matplotlib.text.Text` instances.

          If *autopct* is not *None*, return the tuple (*patches*,
          *texts*, *autotexts*), where *patches* and *texts* are as
          above, and *autotexts* is a list of
          :class:`~matplotlib.text.Text` instances for the numeric
          labels.
        """

        x = np.asarray(x).astype(np.float32)

        sx = float(x.sum())
        if sx > 1:
            x = np.divide(x, sx)

        if labels is None:
            labels = [''] * len(x)
        if explode is None:
            explode = [0] * len(x)
        assert(len(x) == len(labels))
        assert(len(x) == len(explode))
        if colors is None:
            colors = ('b', 'g', 'r', 'c', 'm', 'y', 'k', 'w')

        if radius is None:
            radius = 1

        # Starting theta1 is the start fraction of the circle
        if startangle is None:
            theta1 = 0
        else:
            theta1 = startangle / 360.0

        # set default values in wedge_prop
        if wedgeprops is None:
            wedgeprops = {}
        if 'clip_on' not in wedgeprops:
            wedgeprops['clip_on'] = False

        if textprops is None:
            textprops = {}
        if 'clip_on' not in textprops:
            textprops['clip_on'] = False

        texts = []
        slices = []
        autotexts = []

        i = 0
        for frac, label, expl in cbook.safezip(x, labels, explode):
            x, y = center
            theta2 = (theta1 + frac) if counterclock else (theta1 - frac)
            thetam = 2 * math.pi * 0.5 * (theta1 + theta2)
            x += expl * math.cos(thetam)
            y += expl * math.sin(thetam)

            w = mpatches.Wedge((x, y), radius, 360. * min(theta1, theta2),
                            360. * max(theta1, theta2),
                            facecolor=colors[i % len(colors)],
                            **wedgeprops)
            slices.append(w)
            self.add_patch(w)
            w.set_label(label)

            if shadow:
                # make sure to add a shadow after the call to
                # add_patch so the figure and transform props will be
                # set
                shad = mpatches.Shadow(w, -0.02, -0.02)
                shad.set_zorder(0.9 * w.get_zorder())
                shad.set_label('_nolegend_')
                self.add_patch(shad)

            xt = x + labeldistance * radius * math.cos(thetam)
            yt = y + labeldistance * radius * math.sin(thetam)
            label_alignment = xt > 0 and 'left' or 'right'

            t = self.text(xt, yt, label,
                          size=rcParams['xtick.labelsize'],
                          horizontalalignment=label_alignment,
                          verticalalignment='center',
                          **textprops)

            texts.append(t)

            if autopct is not None:
                xt = x + pctdistance * radius * math.cos(thetam)
                yt = y + pctdistance * radius * math.sin(thetam)
                if is_string_like(autopct):
                    s = autopct % (100. * frac)
                elif six.callable(autopct):
                    s = autopct(100. * frac)
                else:
                    raise TypeError(
                        'autopct must be callable or a format string')

                t = self.text(xt, yt, s,
                              horizontalalignment='center',
                              verticalalignment='center',
                              **textprops)

                autotexts.append(t)

            theta1 = theta2
            i += 1

        if not frame:
            self.set_frame_on(False)

            self.set_xlim((-1.25 + center[0],
                            1.25 + center[0]))
            self.set_ylim((-1.25 + center[1],
                            1.25 + center[1]))
            self.set_xticks([])
            self.set_yticks([])

        if autopct is None:
            return slices, texts
        else:
            return slices, texts, autotexts

    @docstring.dedent_interpd
    def errorbar(self, x, y, yerr=None, xerr=None,
                 fmt='', ecolor=None, elinewidth=None, capsize=3,
                 barsabove=False, lolims=False, uplims=False,
                 xlolims=False, xuplims=False, errorevery=1, capthick=None,
                 **kwargs):
        """
        Plot an errorbar graph.

        Call signature::

          errorbar(x, y, yerr=None, xerr=None,
                   fmt='', ecolor=None, elinewidth=None, capsize=3,
                   barsabove=False, lolims=False, uplims=False,
                   xlolims=False, xuplims=False, errorevery=1,
                   capthick=None)

        Plot *x* versus *y* with error deltas in *yerr* and *xerr*.
        Vertical errorbars are plotted if *yerr* is not *None*.
        Horizontal errorbars are plotted if *xerr* is not *None*.

        *x*, *y*, *xerr*, and *yerr* can all be scalars, which plots a
        single error bar at *x*, *y*.

        Optional keyword arguments:

          *xerr*/*yerr*: [ scalar | N, Nx1, or 2xN array-like ]
            If a scalar number, len(N) array-like object, or an Nx1
            array-like object, errorbars are drawn at +/-value relative
            to the data.

            If a sequence of shape 2xN, errorbars are drawn at -row1
            and +row2 relative to the data.

          *fmt*: [ '' | 'none' | plot format string ]
            The plot format symbol. If *fmt* is 'none' (case-insensitive),
            only the errorbars are plotted.  This is used for adding
            errorbars to a bar plot, for example.  Default is '',
            an empty plot format string; properties are
            then identical to the defaults for :meth:`plot`.

          *ecolor*: [ *None* | mpl color ]
            A matplotlib color arg which gives the color the errorbar lines;
            if *None*, use the color of the line connecting the markers.

          *elinewidth*: scalar
            The linewidth of the errorbar lines. If *None*, use the linewidth.

          *capsize*: scalar
            The length of the error bar caps in points

          *capthick*: scalar
            An alias kwarg to *markeredgewidth* (a.k.a. - *mew*). This
            setting is a more sensible name for the property that
            controls the thickness of the error bar cap in points. For
            backwards compatibility, if *mew* or *markeredgewidth* are given,
            then they will over-ride *capthick*.  This may change in future
            releases.

          *barsabove*: [ *True* | *False* ]
            if *True*, will plot the errorbars above the plot
            symbols. Default is below.

          *lolims* / *uplims* / *xlolims* / *xuplims*: [ *False* | *True* ]
            These arguments can be used to indicate that a value gives
            only upper/lower limits. In that case a caret symbol is
            used to indicate this. lims-arguments may be of the same
            type as *xerr* and *yerr*.  To use limits with inverted
            axes, :meth:`set_xlim` or :meth:`set_ylim` must be called
            before :meth:`errorbar`.

          *errorevery*: positive integer
            subsamples the errorbars. e.g., if everyerror=5, errorbars for
            every 5-th datapoint will be plotted. The data plot itself still
            shows all data points.

        All other keyword arguments are passed on to the plot command for the
        markers. For example, this code makes big red squares with
        thick green edges::

          x,y,yerr = rand(3,10)
          errorbar(x, y, yerr, marker='s',
                   mfc='red', mec='green', ms=20, mew=4)

        where *mfc*, *mec*, *ms* and *mew* are aliases for the longer
        property names, *markerfacecolor*, *markeredgecolor*, *markersize*
        and *markeredgewith*.

        valid kwargs for the marker properties are

        %(Line2D)s

        Returns (*plotline*, *caplines*, *barlinecols*):

            *plotline*: :class:`~matplotlib.lines.Line2D` instance
                *x*, *y* plot markers and/or line

            *caplines*: list of error bar cap
                :class:`~matplotlib.lines.Line2D` instances
            *barlinecols*: list of
                :class:`~matplotlib.collections.LineCollection` instances for
                the horizontal and vertical error ranges.

        **Example:**

        .. plot:: mpl_examples/statistics/errorbar_demo.py

        """

        if errorevery < 1:
            raise ValueError(
                'errorevery has to be a strictly positive integer')

        self._process_unit_info(xdata=x, ydata=y, kwargs=kwargs)
        if not self._hold:
            self.cla()
        holdstate = self._hold
        self._hold = True

        if fmt is None:
            fmt = 'none'
            msg = ('Use of None object as fmt keyword argument to '
                   + 'suppress plotting of data values is deprecated '
                   + 'since 1.4; use the string "none" instead.')
            warnings.warn(msg, mplDeprecation, stacklevel=1)

        plot_line = (fmt.lower() != 'none')

        label = kwargs.pop("label", None)

        # make sure all the args are iterable; use lists not arrays to
        # preserve units
        if not iterable(x):
            x = [x]

        if not iterable(y):
            y = [y]

        if xerr is not None:
            if not iterable(xerr):
                xerr = [xerr] * len(x)

        if yerr is not None:
            if not iterable(yerr):
                yerr = [yerr] * len(y)

        l0 = None

        # Instead of using zorder, the line plot is being added
        # either here, or after all the errorbar plot elements.
        if barsabove and plot_line:
            l0, = self.plot(x, y, fmt, label="_nolegend_", **kwargs)

        barcols = []
        caplines = []

        lines_kw = {'label': '_nolegend_'}
        if elinewidth:
            lines_kw['linewidth'] = elinewidth
        else:
            for key in ('linewidth', 'lw'):
                if key in kwargs:
                    lines_kw[key] = kwargs[key]
        for key in ('transform', 'alpha', 'zorder'):
            if key in kwargs:
                lines_kw[key] = kwargs[key]

        # arrays fine here, they are booleans and hence not units
        if not iterable(lolims):
            lolims = np.asarray([lolims] * len(x), bool)
        else:
            lolims = np.asarray(lolims, bool)

        if not iterable(uplims):
            uplims = np.array([uplims] * len(x), bool)
        else:
            uplims = np.asarray(uplims, bool)

        if not iterable(xlolims):
            xlolims = np.array([xlolims] * len(x), bool)
        else:
            xlolims = np.asarray(xlolims, bool)

        if not iterable(xuplims):
            xuplims = np.array([xuplims] * len(x), bool)
        else:
            xuplims = np.asarray(xuplims, bool)

        everymask = np.arange(len(x)) % errorevery == 0

        def xywhere(xs, ys, mask):
            """
            return xs[mask], ys[mask] where mask is True but xs and
            ys are not arrays
            """
            assert len(xs) == len(ys)
            assert len(xs) == len(mask)
            xs = [thisx for thisx, b in zip(xs, mask) if b]
            ys = [thisy for thisy, b in zip(ys, mask) if b]
            return xs, ys

        plot_kw = {'label': '_nolegend_'}
        if capsize > 0:
            plot_kw['ms'] = 2. * capsize
        if capthick is not None:
            # 'mew' has higher priority, I believe,
            # if both 'mew' and 'markeredgewidth' exists.
            # So, save capthick to markeredgewidth so that
            # explicitly setting mew or markeredgewidth will
            # over-write capthick.
            plot_kw['markeredgewidth'] = capthick
        # For backwards-compat, allow explicit setting of
        # 'mew' or 'markeredgewidth' to over-ride capthick.
        for key in ('markeredgewidth', 'mew', 'transform', 'alpha', 'zorder'):
            if key in kwargs:
                plot_kw[key] = kwargs[key]

        if xerr is not None:
            if (iterable(xerr) and len(xerr) == 2 and
                iterable(xerr[0]) and iterable(xerr[1])):
                # using list comps rather than arrays to preserve units
                left = [thisx - thiserr for (thisx, thiserr)
                        in cbook.safezip(x, xerr[0])]
                right = [thisx + thiserr for (thisx, thiserr)
                         in cbook.safezip(x, xerr[1])]
            else:
                # using list comps rather than arrays to preserve units
                left = [thisx - thiserr for (thisx, thiserr)
                        in cbook.safezip(x, xerr)]
                right = [thisx + thiserr for (thisx, thiserr)
                         in cbook.safezip(x, xerr)]

            # select points without upper/lower limits in x and
            # draw normal errorbars for these points
            noxlims = ~(xlolims | xuplims)
            if noxlims.any():
                yo, _ = xywhere(y, right, noxlims & everymask)
                lo, ro = xywhere(left, right, noxlims & everymask)
                barcols.append(self.hlines(yo, lo, ro, **lines_kw))
                if capsize > 0:
                    caplines.extend(self.plot(lo, yo, 'k|', **plot_kw))
                    caplines.extend(self.plot(ro, yo, 'k|', **plot_kw))

            if xlolims.any():
                yo, _ = xywhere(y, right, xlolims & everymask)
                lo, ro = xywhere(x, right, xlolims & everymask)
                barcols.append(self.hlines(yo, lo, ro, **lines_kw))
                rightup, yup = xywhere(right, y, xlolims & everymask)
                if self.xaxis_inverted():
                    marker = mlines.CARETLEFT
                else:
                    marker = mlines.CARETRIGHT
                caplines.extend(
                    self.plot(rightup, yup, ls='None', marker=marker,
                              **plot_kw))
                if capsize > 0:
                    xlo, ylo = xywhere(x, y, xlolims & everymask)
                    caplines.extend(self.plot(xlo, ylo, 'k|', **plot_kw))

            if xuplims.any():
                yo, _ = xywhere(y, right, xuplims & everymask)
                lo, ro = xywhere(left, x, xuplims & everymask)
                barcols.append(self.hlines(yo, lo, ro, **lines_kw))
                leftlo, ylo = xywhere(left, y, xuplims & everymask)
                if self.xaxis_inverted():
                    marker = mlines.CARETRIGHT
                else:
                    marker = mlines.CARETLEFT
                caplines.extend(
                    self.plot(leftlo,  ylo, ls='None', marker=marker,
                              **plot_kw))
                if capsize > 0:
                    xup, yup = xywhere(x, y, xuplims & everymask)
                    caplines.extend(self.plot(xup, yup, 'k|', **plot_kw))

        if yerr is not None:
            if (iterable(yerr) and len(yerr) == 2 and
                iterable(yerr[0]) and iterable(yerr[1])):
                # using list comps rather than arrays to preserve units
                lower = [thisy - thiserr for (thisy, thiserr)
                         in cbook.safezip(y, yerr[0])]
                upper = [thisy + thiserr for (thisy, thiserr)
                         in cbook.safezip(y, yerr[1])]
            else:
                # using list comps rather than arrays to preserve units
                lower = [thisy - thiserr for (thisy, thiserr)
                         in cbook.safezip(y, yerr)]
                upper = [thisy + thiserr for (thisy, thiserr)
                         in cbook.safezip(y, yerr)]

            # select points without upper/lower limits in y and
            # draw normal errorbars for these points
            noylims = ~(lolims | uplims)
            if noylims.any():
                xo, _ = xywhere(x, lower, noylims & everymask)
                lo, uo = xywhere(lower, upper, noylims & everymask)
                barcols.append(self.vlines(xo, lo, uo, **lines_kw))
                if capsize > 0:
                    caplines.extend(self.plot(xo, lo, 'k_', **plot_kw))
                    caplines.extend(self.plot(xo, uo, 'k_', **plot_kw))

            if lolims.any():
                xo, _ = xywhere(x, lower, lolims & everymask)
                lo, uo = xywhere(y, upper, lolims & everymask)
                barcols.append(self.vlines(xo, lo, uo, **lines_kw))
                xup, upperup = xywhere(x, upper, lolims & everymask)
                if self.yaxis_inverted():
                    marker = mlines.CARETDOWN
                else:
                    marker = mlines.CARETUP
                caplines.extend(
                    self.plot(xup, upperup, ls='None', marker=marker,
                              **plot_kw))
                if capsize > 0:
                    xlo, ylo = xywhere(x, y, lolims & everymask)
                    caplines.extend(self.plot(xlo, ylo, 'k_', **plot_kw))

            if uplims.any():
                xo, _ = xywhere(x, lower, uplims & everymask)
                lo, uo = xywhere(lower, y, uplims & everymask)
                barcols.append(self.vlines(xo, lo, uo, **lines_kw))
                xlo, lowerlo = xywhere(x, lower, uplims & everymask)
                if self.yaxis_inverted():
                    marker = mlines.CARETUP
                else:
                    marker = mlines.CARETDOWN
                caplines.extend(
                    self.plot(xlo, lowerlo, ls='None', marker=marker,
                              **plot_kw))
                if capsize > 0:
                    xup, yup = xywhere(x, y, uplims & everymask)
                    caplines.extend(self.plot(xup, yup, 'k_', **plot_kw))

        if not barsabove and plot_line:
            l0, = self.plot(x, y, fmt, **kwargs)

        if ecolor is None:
            if l0 is None:
                ecolor = six.next(self._get_lines.color_cycle)
            else:
                ecolor = l0.get_color()

        for l in barcols:
            l.set_color(ecolor)
        for l in caplines:
            l.set_color(ecolor)

        self.autoscale_view()
        self._hold = holdstate

        errorbar_container = ErrorbarContainer((l0, tuple(caplines),
                                                tuple(barcols)),
                                               has_xerr=(xerr is not None),
                                               has_yerr=(yerr is not None),
                                               label=label)
        self.containers.append(errorbar_container)

        return errorbar_container  # (l0, caplines, barcols)

    def boxplot(self, x, notch=False, sym=None, vert=True, whis=1.5,
                positions=None, widths=None, patch_artist=False,
                bootstrap=None, usermedians=None, conf_intervals=None,
                meanline=False, showmeans=False, showcaps=True,
                showbox=True, showfliers=True, boxprops=None, labels=None,
                flierprops=None, medianprops=None, meanprops=None,
                capprops=None, whiskerprops=None, manage_xticks=True):
        """
        Make a box and whisker plot.

        Call signature::

          boxplot(self, x, notch=False, sym='b+', vert=True, whis=1.5,
                  positions=None, widths=None, patch_artist=False,
                  bootstrap=None, usermedians=None, conf_intervals=None,
                  meanline=False, showmeans=False, showcaps=True,
                  showbox=True, showfliers=True, boxprops=None, labels=None,
                  flierprops=None, medianprops=None, meanprops=None,
                  capprops=None, whiskerprops=None, manage_xticks=True):

        Make a box and whisker plot for each column of *x* or each
        vector in sequence *x*.  The box extends from the lower to
        upper quartile values of the data, with a line at the median.
        The whiskers extend from the box to show the range of the
        data.  Flier points are those past the end of the whiskers.

        Parameters
        ----------

          x : Array or a sequence of vectors.
            The input data.

          notch : bool, default = False
            If False, produces a rectangular box plot.
            If True, will produce a notched box plot

          sym : str or None, default = None
            The default symbol for flier points.
            Enter an empty string ('') if you don't want to show fliers.
            If `None`, then the fliers default to 'b+'  If you want more
            control use the fliersprop kwarg.

          vert : bool, default = True
            If True (default), makes the boxes vertical.
            If False, makes horizontal boxes.

          whis : float, sequence (default = 1.5) or string
            As a float, determines the reach of the whiskers past the first
            and third quartiles (e.g., Q3 + whis*IQR, IQR = interquartile
            range, Q3-Q1). Beyond the whiskers, data are considered outliers
            and are plotted as individual points. Set this to an unreasonably
            high value to force the whiskers to show the min and max values.
            Alternatively, set this to an ascending sequence of percentile
            (e.g., [5, 95]) to set the whiskers at specific percentiles of
            the data. Finally, *whis* can be the string 'range' to force the
            whiskers to the min and max of the data. In the edge case that
            the 25th and 75th percentiles are equivalent, *whis* will be
            automatically set to 'range'.

          bootstrap : None (default) or integer
            Specifies whether to bootstrap the confidence intervals
            around the median for notched boxplots. If bootstrap==None,
            no bootstrapping is performed, and notches are calculated
            using a Gaussian-based asymptotic approximation  (see McGill, R.,
            Tukey, J.W., and Larsen, W.A., 1978, and Kendall and Stuart,
            1967). Otherwise, bootstrap specifies the number of times to
            bootstrap the median to determine it's 95% confidence intervals.
            Values between 1000 and 10000 are recommended.

          usermedians : array-like or None (default)
            An array or sequence whose first dimension (or length) is
            compatible with *x*. This overrides the medians computed by
            matplotlib for each element of *usermedians* that is not None.
            When an element of *usermedians* == None, the median will be
            computed by matplotlib as normal.

          conf_intervals : array-like or None (default)
            Array or sequence whose first dimension (or length) is compatible
            with *x* and whose second dimension is 2. When the current element
            of *conf_intervals* is not None, the notch locations computed by
            matplotlib are overridden (assuming notch is True). When an
            element of *conf_intervals* is None, boxplot compute notches the
            method specified by the other kwargs (e.g., *bootstrap*).

          positions : array-like, default = [1, 2, ..., n]
            Sets the positions of the boxes. The ticks and limits
            are automatically set to match the positions.

          widths : array-like, default = 0.5
            Either a scalar or a vector and sets the width of each box. The
            default is 0.5, or ``0.15*(distance between extreme positions)``
            if that is smaller.

          labels : sequence or None (default)
                Labels for each dataset. Length must be compatible with
                dimensions  of *x*

          patch_artist : bool, default = False
            If False produces boxes with the Line2D artist
            If True produces boxes with the Patch artist

          showmeans : bool, default = False
            If True, will toggle one the rendering of the means

          showcaps : bool, default = True
            If True, will toggle one the rendering of the caps

          showbox : bool, default = True
            If True, will toggle one the rendering of box

          showfliers : bool, default = True
            If True, will toggle one the rendering of the fliers

          boxprops : dict or None (default)
            If provided, will set the plotting style of the boxes

          whiskerprops : dict or None (default)
            If provided, will set the plotting style of the whiskers

          capprops : dict or None (default)
            If provided, will set the plotting style of the caps

          flierprops : dict or None (default)
            If provided, will set the plotting style of the fliers

          medianprops : dict or None (default)
            If provided, will set the plotting style of the medians

          meanprops : dict or None (default)
            If provided, will set the plotting style of the means

          meanline : bool, default = False
            If True (and *showmeans* is True), will try to render the mean
            as a line spanning the full width of the box according to
            *meanprops*. Not recommended if *shownotches* is also True.
            Otherwise, means will be shown as points.

        Returns
        -------

        result : dict
            A dictionary mapping each component of the boxplot
            to a list of the :class:`matplotlib.lines.Line2D`
            instances created. That dictionary has the following keys
            (assuming vertical boxplots):

            - boxes: the main body of the boxplot showing the quartiles
              and the median's confidence intervals if enabled.
            - medians: horizonal lines at the median of each box.
            - whiskers: the vertical lines extending to the most extreme,
              n-outlier data points.
            - caps: the horizontal lines at the ends of the whiskers.
            - fliers: points representing data that extend beyond the
              whiskers (outliers).
            - means: points or lines representing the means.

        Examples
        --------

        .. plot:: mpl_examples/statistics/boxplot_demo.py
        """
        bxpstats = cbook.boxplot_stats(x, whis=whis, bootstrap=bootstrap,
                                       labels=labels)
        # make sure we have a dictionary
        if flierprops is None:
            flierprops = dict()
        # if non-default sym value, put it into the flier dictionary
        # the logic for providing the default symbol ('b+') now lives
        # in bxp in the initial value of final_flierprops
        # handle all of the `sym` related logic here so we only have to pass
        # on the flierprops dict.
        if sym is not None:
            # no-flier case, which should really be done with
            # 'showfliers=False' but none-the-less deal with it to keep back
            # compatibility
            if sym == '':
                # blow away existing dict and make one for invisible markers
                flierprops = dict(linestyle='none', marker='',
                    color='none')
                # turn the fliers off just to be safe
                showfliers = False
            # now process the symbol string
            else:
                # process the symbol string
                # discarded linestyle
                _, marker, color = _process_plot_format(sym)
                # if we have a marker, use it
                if marker is not None:
                    flierprops['marker'] = marker
                # if we have a color, use it
                if color is not None:
                    # assume that if color is passed in the user want
                    # filled symbol, if the users want more control use
                    # flierprops
                    flierprops['color'] = color

        # replace medians if necessary:
        if usermedians is not None:
            if (len(np.ravel(usermedians)) != len(bxpstats) or
                 np.shape(usermedians)[0] != len(bxpstats)):
                medmsg = 'usermedians length not compatible with x'
                raise ValueError(medmsg)
            else:
                # reassign medians as necessary
                for stats, med in zip(bxpstats, usermedians):
                    if med is not None:
                        stats['med'] = med

        if conf_intervals is not None:
            if np.shape(conf_intervals)[0] != len(bxpstats):
                raise ValueError('conf_intervals length not '
                                 'compatible with x')
            else:
                for stats, ci in zip(bxpstats, conf_intervals):
                    if ci is not None:
                        if len(ci) != 2:
                            raise ValueError('each confidence interval must '
                                             'have two values')
                        else:
                            if ci[0] is not None:
                                stats['cilo'] = ci[0]
                            if ci[1] is not None:
                                stats['cihi'] = ci[1]

        artists = self.bxp(bxpstats, positions=positions, widths=widths,
                           vert=vert, patch_artist=patch_artist,
                           shownotches=notch, showmeans=showmeans,
                           showcaps=showcaps, showbox=showbox,
                           boxprops=boxprops, flierprops=flierprops,
                           medianprops=medianprops, meanprops=meanprops,
                           meanline=meanline, showfliers=showfliers,
                           capprops=capprops, whiskerprops=whiskerprops,
                           manage_xticks=manage_xticks)
        return artists

    def bxp(self, bxpstats, positions=None, widths=None, vert=True,
            patch_artist=False, shownotches=False, showmeans=False,
            showcaps=True, showbox=True, showfliers=True,
            boxprops=None, whiskerprops=None, flierprops=None,
            medianprops=None, capprops=None, meanprops=None,
            meanline=False, manage_xticks=True):
        """
        Drawing function for box and whisker plots.

        Call signature::

          bxp(self, bxpstats, positions=None, widths=None, vert=True,
              patch_artist=False, shownotches=False, showmeans=False,
              showcaps=True, showbox=True, showfliers=True,
              boxprops=None, whiskerprops=None, flierprops=None,
              medianprops=None, capprops=None, meanprops=None,
              meanline=False, manage_xticks=True):

        Make a box and whisker plot for each column of *x* or each
        vector in sequence *x*.  The box extends from the lower to
        upper quartile values of the data, with a line at the median.
        The whiskers extend from the box to show the range of the
        data.  Flier points are those past the end of the whiskers.

        Parameters
        ----------

        bxpstats : list of dicts
          A list of dictionaries containing stats for each boxplot.
          Required keys are:

          - ``med``: The median (scalar float).

          - ``q1``: The first quartile (25th percentile) (scalar
            float).

          - ``q3``: The first quartile (50th percentile) (scalar
            float).

          - ``whislo``: Lower bound of the lower whisker (scalar
            float).

          - ``whishi``: Upper bound of the upper whisker (scalar
            float).

          Optional keys are:

          - ``mean``: The mean (scalar float). Needed if
            ``showmeans=True``.

          - ``fliers``: Data beyond the whiskers (sequence of floats).
            Needed if ``showfliers=True``.

          - ``cilo`` & ``ciho``: Lower and upper confidence intervals
            about the median. Needed if ``shownotches=True``.

          - ``label``: Name of the dataset (string). If available,
            this will be used a tick label for the boxplot

        positions : array-like, default = [1, 2, ..., n]
          Sets the positions of the boxes. The ticks and limits
          are automatically set to match the positions.

        widths : array-like, default = 0.5
          Either a scalar or a vector and sets the width of each
          box. The default is 0.5, or ``0.15*(distance between extreme
          positions)`` if that is smaller.

        vert : bool, default = False
          If `True` (default), makes the boxes vertical.  If `False`,
          makes horizontal boxes.

        patch_artist : bool, default = False
          If `False` produces boxes with the
          `~matplotlib.lines.Line2D` artist.  If `True` produces boxes
          with the `~matplotlib.patches.Patch` artist.

        shownotches : bool, default = False
          If `False` (default), produces a rectangular box plot.
          If `True`, will produce a notched box plot

        showmeans : bool, default = False
          If `True`, will toggle one the rendering of the means

        showcaps  : bool, default = True
          If `True`, will toggle one the rendering of the caps

        showbox  : bool, default = True
          If `True`, will toggle one the rendering of box

        showfliers : bool, default = True
          If `True`, will toggle one the rendering of the fliers

        boxprops : dict or None (default)
          If provided, will set the plotting style of the boxes

        whiskerprops : dict or None (default)
          If provided, will set the plotting style of the whiskers

        capprops : dict or None (default)
          If provided, will set the plotting style of the caps

        flierprops : dict or None (default)
          If provided will set the plotting style of the fliers

        medianprops : dict or None (default)
          If provided, will set the plotting style of the medians

        meanprops : dict or None (default)
          If provided, will set the plotting style of the means

        meanline : bool, default = False
          If `True` (and *showmeans* is `True`), will try to render the mean
          as a line spanning the full width of the box according to
          *meanprops*. Not recommended if *shownotches* is also True.
          Otherwise, means will be shown as points.

        manage_xticks : bool, default = True
          If the function should adjust the xlim and xtick locations.

        Returns
        -------
        result : dict
          A dictionary mapping each component of the boxplot to a list
          of the :class:`matplotlib.lines.Line2D` instances
          created. That dictionary has the following keys (assuming
          vertical boxplots):

          - ``boxes``: the main body of the boxplot showing the
            quartiles and the median's confidence intervals if
            enabled.

          - ``medians``: horizonal lines at the median of each box.

          - ``whiskers``: the vertical lines extending to the most
            extreme, n-outlier data points.

          - ``caps``: the horizontal lines at the ends of the
            whiskers.

          - ``fliers``: points representing data that extend beyond
            the whiskers (fliers).

          - ``means``: points or lines representing the means.

        Examples
        --------

        .. plot:: mpl_examples/statistics/bxp_demo.py

        """
        # lists of artists to be output
        whiskers = []
        caps = []
        boxes = []
        medians = []
        means = []
        fliers = []

        # empty list of xticklabels
        datalabels = []

        # translates between line2D and patch linestyles
        linestyle_map = {
            'solid': '-',
            'dashed': '--',
            'dashdot': '-.',
            'dotted': ':'
        }

        # box properties
        if patch_artist:
            final_boxprops = dict(linestyle='solid', edgecolor='black',
                                  facecolor='white', linewidth=1)
        else:
            final_boxprops = dict(linestyle='-', color='blue')

        if boxprops is not None:
            final_boxprops.update(boxprops)

        # other (cap, whisker) properties
        final_whiskerprops = dict(
            linestyle='--',
            color='blue',
        )

        final_capprops = dict(
            linestyle='-',
            color='black',
        )

        if capprops is not None:
            final_capprops.update(capprops)

        if whiskerprops is not None:
            final_whiskerprops.update(whiskerprops)

        # set up the default flier properties
        final_flierprops = dict(linestyle='none', marker='+', color='blue')

        # flier (outlier) properties
        if flierprops is not None:
            final_flierprops.update(flierprops)

        # median line properties
        final_medianprops = dict(linestyle='-', color='red')
        if medianprops is not None:
            final_medianprops.update(medianprops)

        # mean (line or point) properties
        if meanline:
            final_meanprops = dict(linestyle='--', color='black')
        else:
            final_meanprops = dict(linestyle='none', markerfacecolor='red',
                                   marker='s')
        if meanprops is not None:
            final_meanprops.update(meanprops)

        def to_vc(xs, ys):
            # convert arguments to verts and codes
            verts = []
            #codes = []
            for xi, yi in zip(xs, ys):
                verts.append((xi, yi))
            verts.append((0, 0))  # ignored
            codes = [mpath.Path.MOVETO] + \
                    [mpath.Path.LINETO] * (len(verts) - 2) + \
                    [mpath.Path.CLOSEPOLY]
            return verts, codes

        def patch_list(xs, ys, **kwargs):
            verts, codes = to_vc(xs, ys)
            path = mpath.Path(verts, codes)
            patch = mpatches.PathPatch(path, **kwargs)
            self.add_artist(patch)
            return [patch]

        # vertical or horizontal plot?
        if vert:
            def doplot(*args, **kwargs):
                return self.plot(*args, **kwargs)

            def dopatch(xs, ys, **kwargs):
                return patch_list(xs, ys, **kwargs)

        else:
            def doplot(*args, **kwargs):
                shuffled = []
                for i in xrange(0, len(args), 2):
                    shuffled.extend([args[i + 1], args[i]])
                return self.plot(*shuffled, **kwargs)

            def dopatch(xs, ys, **kwargs):
                xs, ys = ys, xs  # flip X, Y
                return patch_list(xs, ys, **kwargs)

        # input validation
        N = len(bxpstats)
        datashape_message = ("List of boxplot statistics and `{0}` "
                             "values must have same the length")
        # check position
        if positions is None:
            positions = list(xrange(1, N + 1))
        elif len(positions) != N:
            raise ValueError(datashape_message.format("positions"))

        # width
        if widths is None:
            distance = max(positions) - min(positions)
            widths = [min(0.15 * max(distance, 1.0), 0.5)] * N
        elif np.isscalar(widths):
            widths = [widths] * N
        elif len(widths) != N:
            raise ValueError(datashape_message.format("widths"))

        # check and save the `hold` state of the current axes
        if not self._hold:
            self.cla()
        holdStatus = self._hold
        for pos, width, stats in zip(positions, widths, bxpstats):
            # try to find a new label
            datalabels.append(stats.get('label', pos))
            # fliers coords
            flier_x = np.ones(len(stats['fliers'])) * pos
            flier_y = stats['fliers']

            # whisker coords
            whisker_x = np.ones(2) * pos
            whiskerlo_y = np.array([stats['q1'], stats['whislo']])
            whiskerhi_y = np.array([stats['q3'], stats['whishi']])

            # cap coords
            cap_left = pos - width * 0.25
            cap_right = pos + width * 0.25
            cap_x = np.array([cap_left, cap_right])
            cap_lo = np.ones(2) * stats['whislo']
            cap_hi = np.ones(2) * stats['whishi']

            # box and median coords
            box_left = pos - width * 0.5
            box_right = pos + width * 0.5
            med_y = [stats['med'], stats['med']]

            # notched boxes
            if shownotches:
                box_x = [box_left, box_right, box_right, cap_right, box_right,
                         box_right, box_left, box_left, cap_left, box_left,
                         box_left]
                box_y = [stats['q1'], stats['q1'], stats['cilo'],
                         stats['med'], stats['cihi'], stats['q3'],
                         stats['q3'], stats['cihi'], stats['med'],
                         stats['cilo'], stats['q1']]
                med_x = cap_x

            # plain boxes
            else:
                box_x = [box_left, box_right, box_right, box_left, box_left]
                box_y = [stats['q1'], stats['q1'], stats['q3'], stats['q3'],
                         stats['q1']]
                med_x = [box_left, box_right]

            # maybe draw the box:
            if showbox:
                if patch_artist:
                    boxes.extend(dopatch(box_x, box_y, **final_boxprops))
                else:
                    boxes.extend(doplot(box_x, box_y, **final_boxprops))

            # draw the whiskers
            whiskers.extend(doplot(
                whisker_x, whiskerlo_y, **final_whiskerprops
            ))
            whiskers.extend(doplot(
                whisker_x, whiskerhi_y, **final_whiskerprops
            ))

            # maybe draw the caps:
            if showcaps:
                caps.extend(doplot(cap_x, cap_lo, **final_capprops))
                caps.extend(doplot(cap_x, cap_hi, **final_capprops))

            # draw the medians
            medians.extend(doplot(med_x, med_y, **final_medianprops))

            # maybe draw the means
            if showmeans:
                if meanline:
                    means.extend(doplot(
                        [box_left, box_right], [stats['mean'], stats['mean']],
                        **final_meanprops
                    ))
                else:
                    means.extend(doplot(
                        [pos], [stats['mean']], **final_meanprops
                    ))

            # maybe draw the fliers
            if showfliers:
                fliers.extend(doplot(
                    flier_x, flier_y, **final_flierprops
                ))

        # fix our axes/ticks up a little
        if vert:
            setticks = self.set_xticks
            setlim = self.set_xlim
            setlabels = self.set_xticklabels
        else:
            setticks = self.set_yticks
            setlim = self.set_ylim
            setlabels = self.set_yticklabels

        if manage_xticks:
            newlimits = min(positions) - 0.5, max(positions) + 0.5
            setlim(newlimits)
            setticks(positions)
            setlabels(datalabels)

        # reset hold status
        self.hold(holdStatus)

        return dict(whiskers=whiskers, caps=caps, boxes=boxes,
                    medians=medians, fliers=fliers, means=means)

    @docstring.dedent_interpd
    def scatter(self, x, y, s=20, c='b', marker='o', cmap=None, norm=None,
                vmin=None, vmax=None, alpha=None, linewidths=None,
                verts=None, **kwargs):
        """
        Make a scatter plot of x vs y, where x and y are sequence like objects
        of the same lengths.

        Parameters
        ----------
        x, y : array_like, shape (n, )
            Input data

        s : scalar or array_like, shape (n, ), optional, default: 20
            size in points^2.

        c : color or sequence of color, optional, default : 'b'
            `c` can be a single color format string, or a sequence of color
            specifications of length `N`, or a sequence of `N` numbers to be
            mapped to colors using the `cmap` and `norm` specified via kwargs
            (see below). Note that `c` should not be a single numeric RGB or
            RGBA sequence because that is indistinguishable from an array of
            values to be colormapped.  `c` can be a 2-D array in which the
            rows are RGB or RGBA, however.

        marker : `~matplotlib.markers.MarkerStyle`, optional, default: 'o'
            See `~matplotlib.markers` for more information on the different
            styles of markers scatter supports.

        cmap : `~matplotlib.colors.Colormap`, optional, default: None
            A `~matplotlib.colors.Colormap` instance or registered name.
            `cmap` is only used if `c` is an array of floats. If None,
            defaults to rc `image.cmap`.

        norm : `~matplotlib.colors.Normalize`, optional, default: None
            A `~matplotlib.colors.Normalize` instance is used to scale
            luminance data to 0, 1. `norm` is only used if `c` is an array of
            floats. If `None`, use the default :func:`normalize`.

        vmin, vmax : scalar, optional, default: None
            `vmin` and `vmax` are used in conjunction with `norm` to normalize
            luminance data.  If either are `None`, the min and max of the
            color array is used.  Note if you pass a `norm` instance, your
            settings for `vmin` and `vmax` will be ignored.

        alpha : scalar, optional, default: None
            The alpha blending value, between 0 (transparent) and 1 (opaque)

        linewidths : scalar or array_like, optional, default: None
            If None, defaults to (lines.linewidth,).  Note that this is a
            tuple, and if you set the linewidths argument you must set it as a
            sequence of floats, as required by
            `~matplotlib.collections.RegularPolyCollection`.

        Returns
        -------
        paths : `~matplotlib.collections.PathCollection`

        Other parameters
        ----------------
        kwargs : `~matplotlib.collections.Collection` properties

        Notes
        ------
        Any or all of `x`, `y`, `s`, and `c` may be masked arrays, in
        which case all masks will be combined and only unmasked points
        will be plotted.

        Examples
        --------
        .. plot:: mpl_examples/shapes_and_collections/scatter_demo.py

        """

        if not self._hold:
            self.cla()

        self._process_unit_info(xdata=x, ydata=y, kwargs=kwargs)
        x = self.convert_xunits(x)
        y = self.convert_yunits(y)

        # np.ma.ravel yields an ndarray, not a masked array,
        # unless its argument is a masked array.
        x = np.ma.ravel(x)
        y = np.ma.ravel(y)
        if x.size != y.size:
            raise ValueError("x and y must be the same size")

        s = np.ma.ravel(s)  # This doesn't have to match x, y in size.

        c_is_stringy = is_string_like(c) or is_sequence_of_strings(c)
        if not c_is_stringy:
            c = np.asanyarray(c)
            if c.size == x.size:
                c = np.ma.ravel(c)

        x, y, s, c = cbook.delete_masked_points(x, y, s, c)

        scales = s   # Renamed for readability below.

        if c_is_stringy:
            colors = mcolors.colorConverter.to_rgba_array(c, alpha)
        else:
            # The inherent ambiguity is resolved in favor of color
            # mapping, not interpretation as rgb or rgba:
            if c.size == x.size:
                colors = None  # use cmap, norm after collection is created
            else:
                colors = mcolors.colorConverter.to_rgba_array(c, alpha)

        faceted = kwargs.pop('faceted', None)
        edgecolors = kwargs.get('edgecolors', None)
        if faceted is not None:
            cbook.warn_deprecated(
                '1.2', name='faceted', alternative='edgecolor',
                obj_type='option')
            if faceted:
                edgecolors = None
            else:
                edgecolors = 'none'

        # to be API compatible
        if marker is None and not (verts is None):
            marker = (verts, 0)
            verts = None

        marker_obj = mmarkers.MarkerStyle(marker)
        path = marker_obj.get_path().transformed(
            marker_obj.get_transform())
        if not marker_obj.is_filled():
            edgecolors = 'face'

        offsets = np.dstack((x, y))

        collection = mcoll.PathCollection(
                (path,), scales,
                facecolors=colors,
                edgecolors=edgecolors,
                linewidths=linewidths,
                offsets=offsets,
                transOffset=kwargs.pop('transform', self.transData),
                )
        collection.set_transform(mtransforms.IdentityTransform())
        collection.set_alpha(alpha)
        collection.update(kwargs)

        if colors is None:
            if norm is not None:
                assert(isinstance(norm, mcolors.Normalize))
            collection.set_array(np.asarray(c))
            collection.set_cmap(cmap)
            collection.set_norm(norm)

            if vmin is not None or vmax is not None:
                collection.set_clim(vmin, vmax)
            else:
                collection.autoscale_None()

        # The margin adjustment is a hack to deal with the fact that we don't
        # want to transform all the symbols whose scales are in points
        # to data coords to get the exact bounding box for efficiency
        # reasons.  It can be done right if this is deemed important.
        # Also, only bother with this padding if there is anything to draw.
        if self._xmargin < 0.05 and x.size > 0:
            self.set_xmargin(0.05)

        if self._ymargin < 0.05 and x.size > 0:
            self.set_ymargin(0.05)

        self.add_collection(collection)
        self.autoscale_view()

        return collection

    @docstring.dedent_interpd
    def hexbin(self, x, y, C=None, gridsize=100, bins=None,
               xscale='linear', yscale='linear', extent=None,
               cmap=None, norm=None, vmin=None, vmax=None,
               alpha=None, linewidths=None, edgecolors='none',
               reduce_C_function=np.mean, mincnt=None, marginals=False,
               **kwargs):
        """
        Make a hexagonal binning plot.

        Call signature::

           hexbin(x, y, C = None, gridsize = 100, bins = None,
                  xscale = 'linear', yscale = 'linear',
                  cmap=None, norm=None, vmin=None, vmax=None,
                  alpha=None, linewidths=None, edgecolors='none'
                  reduce_C_function = np.mean, mincnt=None, marginals=True
                  **kwargs)

        Make a hexagonal binning plot of *x* versus *y*, where *x*,
        *y* are 1-D sequences of the same length, *N*. If *C* is *None*
        (the default), this is a histogram of the number of occurences
        of the observations at (x[i],y[i]).

        If *C* is specified, it specifies values at the coordinate
        (x[i],y[i]). These values are accumulated for each hexagonal
        bin and then reduced according to *reduce_C_function*, which
        defaults to numpy's mean function (np.mean). (If *C* is
        specified, it must also be a 1-D sequence of the same length
        as *x* and *y*.)

        *x*, *y* and/or *C* may be masked arrays, in which case only
        unmasked points will be plotted.

        Optional keyword arguments:

        *gridsize*: [ 100 | integer ]
           The number of hexagons in the *x*-direction, default is
           100. The corresponding number of hexagons in the
           *y*-direction is chosen such that the hexagons are
           approximately regular. Alternatively, gridsize can be a
           tuple with two elements specifying the number of hexagons
           in the *x*-direction and the *y*-direction.

        *bins*: [ *None* | 'log' | integer | sequence ]
           If *None*, no binning is applied; the color of each hexagon
           directly corresponds to its count value.

           If 'log', use a logarithmic scale for the color
           map. Internally, :math:`log_{10}(i+1)` is used to
           determine the hexagon color.

           If an integer, divide the counts in the specified number
           of bins, and color the hexagons accordingly.

           If a sequence of values, the values of the lower bound of
           the bins to be used.

        *xscale*: [ 'linear' | 'log' ]
           Use a linear or log10 scale on the horizontal axis.

        *scale*: [ 'linear' | 'log' ]
           Use a linear or log10 scale on the vertical axis.

        *mincnt*: [ *None* | a positive integer ]
           If not *None*, only display cells with more than *mincnt*
           number of points in the cell

        *marginals*: [ *True* | *False* ]
           if marginals is *True*, plot the marginal density as
           colormapped rectagles along the bottom of the x-axis and
           left of the y-axis

        *extent*: [ *None* | scalars (left, right, bottom, top) ]
           The limits of the bins. The default assigns the limits
           based on gridsize, x, y, xscale and yscale.

        Other keyword arguments controlling color mapping and normalization
        arguments:

        *cmap*: [ *None* | Colormap ]
           a :class:`matplotlib.colors.Colormap` instance. If *None*,
           defaults to rc ``image.cmap``.

        *norm*: [ *None* | Normalize ]
           :class:`matplotlib.colors.Normalize` instance is used to
           scale luminance data to 0,1.

        *vmin* / *vmax*: scalar
           *vmin* and *vmax* are used in conjunction with *norm* to normalize
           luminance data.  If either are *None*, the min and max of the color
           array *C* is used.  Note if you pass a norm instance, your settings
           for *vmin* and *vmax* will be ignored.

        *alpha*: scalar between 0 and 1, or *None*
           the alpha value for the patches

        *linewidths*: [ *None* | scalar ]
           If *None*, defaults to rc lines.linewidth. Note that this
           is a tuple, and if you set the linewidths argument you
           must set it as a sequence of floats, as required by
           :class:`~matplotlib.collections.RegularPolyCollection`.

        Other keyword arguments controlling the Collection properties:

        *edgecolors*: [ *None* | ``'none'`` | mpl color | color sequence ]
           If ``'none'``, draws the edges in the same color as the fill color.
           This is the default, as it avoids unsightly unpainted pixels
           between the hexagons.

           If *None*, draws the outlines in the default color.

           If a matplotlib color arg or sequence of rgba tuples, draws the
           outlines in the specified color.

        Here are the standard descriptions of all the
        :class:`~matplotlib.collections.Collection` kwargs:

        %(Collection)s

        The return value is a
        :class:`~matplotlib.collections.PolyCollection` instance; use
        :meth:`~matplotlib.collections.PolyCollection.get_array` on
        this :class:`~matplotlib.collections.PolyCollection` to get
        the counts in each hexagon. If *marginals* is *True*, horizontal
        bar and vertical bar (both PolyCollections) will be attached
        to the return collection as attributes *hbar* and *vbar*.


        **Example:**

        .. plot:: mpl_examples/pylab_examples/hexbin_demo.py

        """

        if not self._hold:
            self.cla()

        self._process_unit_info(xdata=x, ydata=y, kwargs=kwargs)

        x, y, C = cbook.delete_masked_points(x, y, C)

        # Set the size of the hexagon grid
        if iterable(gridsize):
            nx, ny = gridsize
        else:
            nx = gridsize
            ny = int(nx / math.sqrt(3))
        # Count the number of data in each hexagon
        x = np.array(x, float)
        y = np.array(y, float)
        if xscale == 'log':
            if np.any(x <= 0.0):
                raise ValueError("x contains non-positive values, so can not"
                                 " be log-scaled")
            x = np.log10(x)
        if yscale == 'log':
            if np.any(y <= 0.0):
                raise ValueError("y contains non-positive values, so can not"
                                 " be log-scaled")
            y = np.log10(y)
        if extent is not None:
            xmin, xmax, ymin, ymax = extent
        else:
            xmin = np.amin(x)
            xmax = np.amax(x)
            ymin = np.amin(y)
            ymax = np.amax(y)
            # to avoid issues with singular data, expand the min/max pairs
            xmin, xmax = mtrans.nonsingular(xmin, xmax, expander=0.1)
            ymin, ymax = mtrans.nonsingular(ymin, ymax, expander=0.1)

        # In the x-direction, the hexagons exactly cover the region from
        # xmin to xmax. Need some padding to avoid roundoff errors.
        padding = 1.e-9 * (xmax - xmin)
        xmin -= padding
        xmax += padding
        sx = (xmax - xmin) / nx
        sy = (ymax - ymin) / ny

        if marginals:
            xorig = x.copy()
            yorig = y.copy()

        x = (x - xmin) / sx
        y = (y - ymin) / sy
        ix1 = np.round(x).astype(int)
        iy1 = np.round(y).astype(int)
        ix2 = np.floor(x).astype(int)
        iy2 = np.floor(y).astype(int)

        nx1 = nx + 1
        ny1 = ny + 1
        nx2 = nx
        ny2 = ny
        n = nx1 * ny1 + nx2 * ny2

        d1 = (x - ix1) ** 2 + 3.0 * (y - iy1) ** 2
        d2 = (x - ix2 - 0.5) ** 2 + 3.0 * (y - iy2 - 0.5) ** 2
        bdist = (d1 < d2)
        if C is None:
            accum = np.zeros(n)
            # Create appropriate views into "accum" array.
            lattice1 = accum[:nx1 * ny1]
            lattice2 = accum[nx1 * ny1:]
            lattice1.shape = (nx1, ny1)
            lattice2.shape = (nx2, ny2)

            for i in xrange(len(x)):
                if bdist[i]:
                    if ((ix1[i] >= 0) and (ix1[i] < nx1) and
                        (iy1[i] >= 0) and (iy1[i] < ny1)):
                        lattice1[ix1[i], iy1[i]] += 1
                else:
                    if ((ix2[i] >= 0) and (ix2[i] < nx2) and
                        (iy2[i] >= 0) and (iy2[i] < ny2)):
                        lattice2[ix2[i], iy2[i]] += 1

            # threshold
            if mincnt is not None:
                for i in xrange(nx1):
                    for j in xrange(ny1):
                        if lattice1[i, j] < mincnt:
                            lattice1[i, j] = np.nan
                for i in xrange(nx2):
                    for j in xrange(ny2):
                        if lattice2[i, j] < mincnt:
                            lattice2[i, j] = np.nan
            accum = np.hstack((lattice1.astype(float).ravel(),
                               lattice2.astype(float).ravel()))
            good_idxs = ~np.isnan(accum)

        else:
            if mincnt is None:
                mincnt = 0

            # create accumulation arrays
            lattice1 = np.empty((nx1, ny1), dtype=object)
            for i in xrange(nx1):
                for j in xrange(ny1):
                    lattice1[i, j] = []
            lattice2 = np.empty((nx2, ny2), dtype=object)
            for i in xrange(nx2):
                for j in xrange(ny2):
                    lattice2[i, j] = []

            for i in xrange(len(x)):
                if bdist[i]:
                    if ((ix1[i] >= 0) and (ix1[i] < nx1) and
                        (iy1[i] >= 0) and (iy1[i] < ny1)):
                        lattice1[ix1[i], iy1[i]].append(C[i])
                else:
                    if ((ix2[i] >= 0) and (ix2[i] < nx2) and
                        (iy2[i] >= 0) and (iy2[i] < ny2)):
                        lattice2[ix2[i], iy2[i]].append(C[i])

            for i in xrange(nx1):
                for j in xrange(ny1):
                    vals = lattice1[i, j]
                    if len(vals) > mincnt:
                        lattice1[i, j] = reduce_C_function(vals)
                    else:
                        lattice1[i, j] = np.nan
            for i in xrange(nx2):
                for j in xrange(ny2):
                    vals = lattice2[i, j]
                    if len(vals) > mincnt:
                        lattice2[i, j] = reduce_C_function(vals)
                    else:
                        lattice2[i, j] = np.nan

            accum = np.hstack((lattice1.astype(float).ravel(),
                               lattice2.astype(float).ravel()))
            good_idxs = ~np.isnan(accum)

        offsets = np.zeros((n, 2), float)
        offsets[:nx1 * ny1, 0] = np.repeat(np.arange(nx1), ny1)
        offsets[:nx1 * ny1, 1] = np.tile(np.arange(ny1), nx1)
        offsets[nx1 * ny1:, 0] = np.repeat(np.arange(nx2) + 0.5, ny2)
        offsets[nx1 * ny1:, 1] = np.tile(np.arange(ny2), nx2) + 0.5
        offsets[:, 0] *= sx
        offsets[:, 1] *= sy
        offsets[:, 0] += xmin
        offsets[:, 1] += ymin
        # remove accumulation bins with no data
        offsets = offsets[good_idxs, :]
        accum = accum[good_idxs]

        polygon = np.zeros((6, 2), float)
        polygon[:, 0] = sx * np.array([0.5, 0.5, 0.0, -0.5, -0.5, 0.0])
        polygon[:, 1] = sy * np.array([-0.5, 0.5, 1.0, 0.5, -0.5, -1.0]) / 3.0

        if edgecolors == 'none':
            edgecolors = 'face'

        if xscale == 'log' or yscale == 'log':
            polygons = np.expand_dims(polygon, 0) + np.expand_dims(offsets, 1)
            if xscale == 'log':
                polygons[:, :, 0] = 10.0 ** polygons[:, :, 0]
                xmin = 10.0 ** xmin
                xmax = 10.0 ** xmax
                self.set_xscale(xscale)
            if yscale == 'log':
                polygons[:, :, 1] = 10.0 ** polygons[:, :, 1]
                ymin = 10.0 ** ymin
                ymax = 10.0 ** ymax
                self.set_yscale(yscale)
            collection = mcoll.PolyCollection(
                polygons,
                edgecolors=edgecolors,
                linewidths=linewidths,
                )
        else:
            collection = mcoll.PolyCollection(
                [polygon],
                edgecolors=edgecolors,
                linewidths=linewidths,
                offsets=offsets,
                transOffset=mtransforms.IdentityTransform(),
                offset_position="data"
                )

        if isinstance(norm, mcolors.LogNorm):
            if (accum == 0).any():
                # make sure we have not zeros
                accum += 1

        # autoscale the norm with curren accum values if it hasn't
        # been set
        if norm is not None:
            if norm.vmin is None and norm.vmax is None:
                norm.autoscale(accum)

        # Transform accum if needed
        if bins == 'log':
            accum = np.log10(accum + 1)
        elif bins is not None:
            if not iterable(bins):
                minimum, maximum = min(accum), max(accum)
                bins -= 1  # one less edge than bins
                bins = minimum + (maximum - minimum) * np.arange(bins) / bins
            bins = np.sort(bins)
            accum = bins.searchsorted(accum)

        if norm is not None:
            assert(isinstance(norm, mcolors.Normalize))
        collection.set_array(accum)
        collection.set_cmap(cmap)
        collection.set_norm(norm)
        collection.set_alpha(alpha)
        collection.update(kwargs)

        if vmin is not None or vmax is not None:
            collection.set_clim(vmin, vmax)
        else:
            collection.autoscale_None()

        corners = ((xmin, ymin), (xmax, ymax))
        self.update_datalim(corners)
        self.autoscale_view(tight=True)

        # add the collection last
        self.add_collection(collection, autolim=False)
        if not marginals:
            return collection

        if C is None:
            C = np.ones(len(x))

        def coarse_bin(x, y, coarse):
            ind = coarse.searchsorted(x).clip(0, len(coarse) - 1)
            mus = np.zeros(len(coarse))
            for i in range(len(coarse)):
                mu = reduce_C_function(y[ind == i])
                mus[i] = mu
            return mus

        coarse = np.linspace(xmin, xmax, gridsize)

        xcoarse = coarse_bin(xorig, C, coarse)
        valid = ~np.isnan(xcoarse)
        verts, values = [], []
        for i, val in enumerate(xcoarse):
            thismin = coarse[i]
            if i < len(coarse) - 1:
                thismax = coarse[i + 1]
            else:
                thismax = thismin + np.diff(coarse)[-1]

            if not valid[i]:
                continue

            verts.append([(thismin, 0),
                          (thismin, 0.05),
                          (thismax, 0.05),
                          (thismax, 0)])
            values.append(val)

        values = np.array(values)
        trans = self.get_xaxis_transform(which='grid')

        hbar = mcoll.PolyCollection(verts, transform=trans, edgecolors='face')

        hbar.set_array(values)
        hbar.set_cmap(cmap)
        hbar.set_norm(norm)
        hbar.set_alpha(alpha)
        hbar.update(kwargs)
        self.add_collection(hbar, autolim=False)

        coarse = np.linspace(ymin, ymax, gridsize)
        ycoarse = coarse_bin(yorig, C, coarse)
        valid = ~np.isnan(ycoarse)
        verts, values = [], []
        for i, val in enumerate(ycoarse):
            thismin = coarse[i]
            if i < len(coarse) - 1:
                thismax = coarse[i + 1]
            else:
                thismax = thismin + np.diff(coarse)[-1]
            if not valid[i]:
                continue
            verts.append([(0, thismin), (0.0, thismax),
                          (0.05, thismax), (0.05, thismin)])
            values.append(val)

        values = np.array(values)

        trans = self.get_yaxis_transform(which='grid')

        vbar = mcoll.PolyCollection(verts, transform=trans, edgecolors='face')
        vbar.set_array(values)
        vbar.set_cmap(cmap)
        vbar.set_norm(norm)
        vbar.set_alpha(alpha)
        vbar.update(kwargs)
        self.add_collection(vbar, autolim=False)

        collection.hbar = hbar
        collection.vbar = vbar

        def on_changed(collection):
            hbar.set_cmap(collection.get_cmap())
            hbar.set_clim(collection.get_clim())
            vbar.set_cmap(collection.get_cmap())
            vbar.set_clim(collection.get_clim())

        collection.callbacksSM.connect('changed', on_changed)

        return collection

    @docstring.dedent_interpd
    def arrow(self, x, y, dx, dy, **kwargs):
        """
        Add an arrow to the axes.

        Call signature::

           arrow(x, y, dx, dy, **kwargs)

        Draws arrow on specified axis from (*x*, *y*) to (*x* + *dx*,
        *y* + *dy*). Uses FancyArrow patch to construct the arrow.

        The resulting arrow is affected by the axes aspect ratio and limits.
        This may produce an arrow whose head is not square with its stem. To
        create an arrow whose head is square with its stem, use
        :meth:`annotate` for example::

            ax.annotate("", xy=(0.5, 0.5), xytext=(0, 0),
                arrowprops=dict(arrowstyle="->"))

        Optional kwargs control the arrow construction and properties:

        %(FancyArrow)s

        **Example:**

        .. plot:: mpl_examples/pylab_examples/arrow_demo.py
        """
        # Strip away units for the underlying patch since units
        # do not make sense to most patch-like code
        x = self.convert_xunits(x)
        y = self.convert_yunits(y)
        dx = self.convert_xunits(dx)
        dy = self.convert_yunits(dy)

        a = mpatches.FancyArrow(x, y, dx, dy, **kwargs)
        self.add_artist(a)
        return a

    def quiverkey(self, *args, **kw):
        qk = mquiver.QuiverKey(*args, **kw)
        self.add_artist(qk)
        return qk
    quiverkey.__doc__ = mquiver.QuiverKey.quiverkey_doc

    def quiver(self, *args, **kw):
        if not self._hold:
            self.cla()
        q = mquiver.Quiver(self, *args, **kw)

        self.add_collection(q, autolim=True)
        self.autoscale_view()
        return q
    quiver.__doc__ = mquiver.Quiver.quiver_doc

    def stackplot(self, x, *args, **kwargs):
        return mstack.stackplot(self, x, *args, **kwargs)
    stackplot.__doc__ = mstack.stackplot.__doc__

    def streamplot(self, x, y, u, v, density=1, linewidth=None, color=None,
                   cmap=None, norm=None, arrowsize=1, arrowstyle='-|>',
                   minlength=0.1, transform=None, zorder=1):
        if not self._hold:
            self.cla()
        stream_container = mstream.streamplot(self, x, y, u, v,
                                              density=density,
                                              linewidth=linewidth,
                                              color=color,
                                              cmap=cmap,
                                              norm=norm,
                                              arrowsize=arrowsize,
                                              arrowstyle=arrowstyle,
                                              minlength=minlength,
                                              transform=transform,
                                              zorder=zorder)
        return stream_container
    streamplot.__doc__ = mstream.streamplot.__doc__

    @docstring.dedent_interpd
    def barbs(self, *args, **kw):
        """
        %(barbs_doc)s

        **Example:**

        .. plot:: mpl_examples/pylab_examples/barb_demo.py
        """
        if not self._hold:
            self.cla()
        b = mquiver.Barbs(self, *args, **kw)
        self.add_collection(b, autolim=True)
        self.autoscale_view()
        return b

    @docstring.dedent_interpd
    def fill(self, *args, **kwargs):
        """
        Plot filled polygons.

        Call signature::

          fill(*args, **kwargs)

        *args* is a variable length argument, allowing for multiple
        *x*, *y* pairs with an optional color format string; see
        :func:`~matplotlib.pyplot.plot` for details on the argument
        parsing.  For example, to plot a polygon with vertices at *x*,
        *y* in blue.::

          ax.fill(x,y, 'b' )

        An arbitrary number of *x*, *y*, *color* groups can be specified::

          ax.fill(x1, y1, 'g', x2, y2, 'r')

        Return value is a list of :class:`~matplotlib.patches.Patch`
        instances that were added.

        The same color strings that :func:`~matplotlib.pyplot.plot`
        supports are supported by the fill format string.

        If you would like to fill below a curve, e.g., shade a region
        between 0 and *y* along *x*, use :meth:`fill_between`

        The *closed* kwarg will close the polygon when *True* (default).

        kwargs control the :class:`~matplotlib.patches.Polygon` properties:

        %(Polygon)s

        **Example:**

        .. plot:: mpl_examples/lines_bars_and_markers/fill_demo.py

        """
        if not self._hold:
            self.cla()

        patches = []
        for poly in self._get_patches_for_fill(*args, **kwargs):
            self.add_patch(poly)
            patches.append(poly)
        self.autoscale_view()
        return patches

    @docstring.dedent_interpd
    def fill_between(self, x, y1, y2=0, where=None, interpolate=False,
                     **kwargs):
        """
        Make filled polygons between two curves.

        Call signature::

          fill_between(x, y1, y2=0, where=None, **kwargs)

        Create a :class:`~matplotlib.collections.PolyCollection`
        filling the regions between *y1* and *y2* where
        ``where==True``

          *x* :
            An N-length array of the x data

          *y1* :
            An N-length array (or scalar) of the y data

          *y2* :
            An N-length array (or scalar) of the y data

          *where* :
            If *None*, default to fill between everywhere.  If not *None*,
            it is an N-length numpy boolean array and the fill will
            only happen over the regions where ``where==True``.

          *interpolate* :
            If *True*, interpolate between the two lines to find the
            precise point of intersection.  Otherwise, the start and
            end points of the filled region will only occur on explicit
            values in the *x* array.

          *kwargs* :
            Keyword args passed on to the
            :class:`~matplotlib.collections.PolyCollection`.

        kwargs control the :class:`~matplotlib.patches.Polygon` properties:

        %(PolyCollection)s

        .. plot:: mpl_examples/pylab_examples/fill_between_demo.py

        .. seealso::

            :meth:`fill_betweenx`
                for filling between two sets of x-values

        """
        # Handle united data, such as dates
        self._process_unit_info(xdata=x, ydata=y1, kwargs=kwargs)
        self._process_unit_info(ydata=y2)

        # Convert the arrays so we can work with them
        x = ma.masked_invalid(self.convert_xunits(x))
        y1 = ma.masked_invalid(self.convert_yunits(y1))
        y2 = ma.masked_invalid(self.convert_yunits(y2))

        if y1.ndim == 0:
            y1 = np.ones_like(x) * y1
        if y2.ndim == 0:
            y2 = np.ones_like(x) * y2

        if where is None:
            where = np.ones(len(x), np.bool)
        else:
            where = np.asarray(where, np.bool)

        if not (x.shape == y1.shape == y2.shape == where.shape):
            raise ValueError("Argument dimensions are incompatible")

        mask = reduce(ma.mask_or, [ma.getmask(a) for a in (x, y1, y2)])
        if mask is not ma.nomask:
            where &= ~mask

        polys = []
        for ind0, ind1 in mlab.contiguous_regions(where):
            xslice = x[ind0:ind1]
            y1slice = y1[ind0:ind1]
            y2slice = y2[ind0:ind1]

            if not len(xslice):
                continue

            N = len(xslice)
            X = np.zeros((2 * N + 2, 2), np.float)

            if interpolate:
                def get_interp_point(ind):
                    im1 = max(ind - 1, 0)
                    x_values = x[im1:ind + 1]
                    diff_values = y1[im1:ind + 1] - y2[im1:ind + 1]
                    y1_values = y1[im1:ind + 1]

                    if len(diff_values) == 2:
                        if np.ma.is_masked(diff_values[1]):
                            return x[im1], y1[im1]
                        elif np.ma.is_masked(diff_values[0]):
                            return x[ind], y1[ind]

                    diff_order = diff_values.argsort()
                    diff_root_x = np.interp(
                        0, diff_values[diff_order], x_values[diff_order])
                    diff_root_y = np.interp(diff_root_x, x_values, y1_values)
                    return diff_root_x, diff_root_y

                start = get_interp_point(ind0)
                end = get_interp_point(ind1)
            else:
                # the purpose of the next two lines is for when y2 is a
                # scalar like 0 and we want the fill to go all the way
                # down to 0 even if none of the y1 sample points do
                start = xslice[0], y2slice[0]
                end = xslice[-1], y2slice[-1]

            X[0] = start
            X[N + 1] = end

            X[1:N + 1, 0] = xslice
            X[1:N + 1, 1] = y1slice
            X[N + 2:, 0] = xslice[::-1]
            X[N + 2:, 1] = y2slice[::-1]

            polys.append(X)

        collection = mcoll.PolyCollection(polys, **kwargs)

        # now update the datalim and autoscale
        XY1 = np.array([x[where], y1[where]]).T
        XY2 = np.array([x[where], y2[where]]).T
        self.dataLim.update_from_data_xy(XY1, self.ignore_existing_data_limits,
                                         updatex=True, updatey=True)
        self.ignore_existing_data_limits = False
        self.dataLim.update_from_data_xy(XY2, self.ignore_existing_data_limits,
                                         updatex=False, updatey=True)
        self.add_collection(collection, autolim=False)
        self.autoscale_view()
        return collection

    @docstring.dedent_interpd
    def fill_betweenx(self, y, x1, x2=0, where=None, **kwargs):
        """
        Make filled polygons between two horizontal curves.

        Call signature::

          fill_betweenx(y, x1, x2=0, where=None, **kwargs)

        Create a :class:`~matplotlib.collections.PolyCollection`
        filling the regions between *x1* and *x2* where
        ``where==True``

          *y* :
            An N-length array of the y data

          *x1* :
            An N-length array (or scalar) of the x data

          *x2* :
            An N-length array (or scalar) of the x data

          *where* :
             If *None*, default to fill between everywhere.  If not *None*,
             it is a N length numpy boolean array and the fill will
             only happen over the regions where ``where==True``

          *kwargs* :
            keyword args passed on to the
            :class:`~matplotlib.collections.PolyCollection`

        kwargs control the :class:`~matplotlib.patches.Polygon` properties:

        %(PolyCollection)s

        .. plot:: mpl_examples/pylab_examples/fill_betweenx_demo.py

        .. seealso::

            :meth:`fill_between`
                for filling between two sets of y-values

        """
        # Handle united data, such as dates
        self._process_unit_info(ydata=y, xdata=x1, kwargs=kwargs)
        self._process_unit_info(xdata=x2)

        # Convert the arrays so we can work with them
        y = ma.masked_invalid(self.convert_yunits(y))
        x1 = ma.masked_invalid(self.convert_xunits(x1))
        x2 = ma.masked_invalid(self.convert_xunits(x2))

        if x1.ndim == 0:
            x1 = np.ones_like(y) * x1
        if x2.ndim == 0:
            x2 = np.ones_like(y) * x2

        if where is None:
            where = np.ones(len(y), np.bool)
        else:
            where = np.asarray(where, np.bool)

        if not (y.shape == x1.shape == x2.shape == where.shape):
            raise ValueError("Argument dimensions are incompatible")

        mask = reduce(ma.mask_or, [ma.getmask(a) for a in (y, x1, x2)])
        if mask is not ma.nomask:
            where &= ~mask

        polys = []
        for ind0, ind1 in mlab.contiguous_regions(where):
            yslice = y[ind0:ind1]
            x1slice = x1[ind0:ind1]
            x2slice = x2[ind0:ind1]

            if not len(yslice):
                continue

            N = len(yslice)
            Y = np.zeros((2 * N + 2, 2), np.float)

            # the purpose of the next two lines is for when x2 is a
            # scalar like 0 and we want the fill to go all the way
            # down to 0 even if none of the x1 sample points do
            Y[0] = x2slice[0], yslice[0]
            Y[N + 1] = x2slice[-1], yslice[-1]

            Y[1:N + 1, 0] = x1slice
            Y[1:N + 1, 1] = yslice
            Y[N + 2:, 0] = x2slice[::-1]
            Y[N + 2:, 1] = yslice[::-1]

            polys.append(Y)

        collection = mcoll.PolyCollection(polys, **kwargs)

        # now update the datalim and autoscale
        X1Y = np.array([x1[where], y[where]]).T
        X2Y = np.array([x2[where], y[where]]).T
        self.dataLim.update_from_data_xy(X1Y, self.ignore_existing_data_limits,
                                         updatex=True, updatey=True)
        self.ignore_existing_data_limits = False
        self.dataLim.update_from_data_xy(X2Y, self.ignore_existing_data_limits,
                                         updatex=True, updatey=False)
        self.add_collection(collection, autolim=False)
        self.autoscale_view()
        return collection

    #### plotting z(x,y): imshow, pcolor and relatives, contour

    @docstring.dedent_interpd
    def imshow(self, X, cmap=None, norm=None, aspect=None,
               interpolation=None, alpha=None, vmin=None, vmax=None,
               origin=None, extent=None, shape=None, filternorm=1,
               filterrad=4.0, imlim=None, resample=None, url=None, **kwargs):
        """
        Display an image on the axes.

        Parameters
        -----------
        X : array_like, shape (n, m) or (n, m, 3) or (n, m, 4)
            Display the image in `X` to current axes.  `X` may be a float
            array, a uint8 array or a PIL image. If `X` is an array, it
            can have the following shapes:

            - MxN -- luminance (grayscale, float array only)
            - MxNx3 -- RGB (float or uint8 array)
            - MxNx4 -- RGBA (float or uint8 array)

            The value for each component of MxNx3 and MxNx4 float arrays
            should be in the range 0.0 to 1.0; MxN float arrays may be
            normalised.

        cmap : `~matplotlib.colors.Colormap`, optional, default: None
            If None, default to rc `image.cmap` value. `cmap` is ignored when
            `X` has RGB(A) information

        aspect : ['auto' | 'equal' | scalar], optional, default: None
            If 'auto', changes the image aspect ratio to match that of the
            axes.

            If 'equal', and `extent` is None, changes the axes aspect ratio to
            match that of the image. If `extent` is not `None`, the axes
            aspect ratio is changed to match that of the extent.

            If None, default to rc ``image.aspect`` value.

        interpolation : string, optional, default: None
            Acceptable values are 'none', 'nearest', 'bilinear', 'bicubic',
            'spline16', 'spline36', 'hanning', 'hamming', 'hermite', 'kaiser',
            'quadric', 'catrom', 'gaussian', 'bessel', 'mitchell', 'sinc',
            'lanczos'

            If `interpolation` is None, default to rc `image.interpolation`.
            See also the `filternorm` and `filterrad` parameters.
            If `interpolation` is 'none', then no interpolation is performed
            on the Agg, ps and pdf backends. Other backends will fall back to
            'nearest'.

        norm : `~matplotlib.colors.Normalize`, optional, default: None
            A `~matplotlib.colors.Normalize` instance is used to scale
            luminance data to 0, 1. If `None`, use the default
            func:`normalize`. `norm` is only used if `X` is an array of
            floats.

        vmin, vmax : scalar, optional, default: None
            `vmin` and `vmax` are used in conjunction with norm to normalize
            luminance data.  Note if you pass a `norm` instance, your
            settings for `vmin` and `vmax` will be ignored.

        alpha : scalar, optional, default: None
            The alpha blending value, between 0 (transparent) and 1 (opaque)

        origin : ['upper' | 'lower'], optional, default: None
            Place the [0,0] index of the array in the upper left or lower left
            corner of the axes. If None, default to rc `image.origin`.

        extent : scalars (left, right, bottom, top), optional, default: None
            The location, in data-coordinates, of the lower-left and
            upper-right corners. If `None`, the image is positioned such that
            the pixel centers fall on zero-based (row, column) indices.

        shape : scalars (columns, rows), optional, default: None
            For raw buffer images

        filternorm : scalar, optional, default: 1
            A parameter for the antigrain image resize filter.  From the
            antigrain documentation, if `filternorm` = 1, the filter
            normalizes integer values and corrects the rounding errors. It
            doesn't do anything with the source floating point values, it
            corrects only integers according to the rule of 1.0 which means
            that any sum of pixel weights must be equal to 1.0.  So, the
            filter function must produce a graph of the proper shape.

        filterrad : scalar, optional, default: 4.0
            The filter radius for filters that have a radius parameter, i.e.
            when interpolation is one of: 'sinc', 'lanczos' or 'blackman'

        Returns
        --------
        image : `~matplotlib.image.AxesImage`

        Other parameters
        ----------------
        kwargs : `~matplotlib.artist.Artist` properties.

        See also
        --------
        matshow : Plot a matrix or an array as an image.

        Examples
        --------

        .. plot:: mpl_examples/pylab_examples/image_demo.py

        """

        if not self._hold:
            self.cla()

        if norm is not None:
            assert(isinstance(norm, mcolors.Normalize))
        if aspect is None:
            aspect = rcParams['image.aspect']
        self.set_aspect(aspect)
        im = mimage.AxesImage(self, cmap, norm, interpolation, origin, extent,
                       filternorm=filternorm,
                       filterrad=filterrad, resample=resample, **kwargs)

        im.set_data(X)
        im.set_alpha(alpha)
        if im.get_clip_path() is None:
            # image does not already have clipping set, clip to axes patch
            im.set_clip_path(self.patch)
        #if norm is None and shape is None:
        #    im.set_clim(vmin, vmax)
        if vmin is not None or vmax is not None:
            im.set_clim(vmin, vmax)
        else:
            im.autoscale_None()
        im.set_url(url)

        # update ax.dataLim, and, if autoscaling, set viewLim
        # to tightly fit the image, regardless of dataLim.
        im.set_extent(im.get_extent())

        self.add_image(im)
        return im

    @staticmethod
    def _pcolorargs(funcname, *args, **kw):
        # This takes one kwarg, allmatch.
        # If allmatch is True, then the incoming X, Y, C must
        # have matching dimensions, taking into account that
        # X and Y can be 1-D rather than 2-D.  This perfect
        # match is required for Gouroud shading.  For flat
        # shading, X and Y specify boundaries, so we need
        # one more boundary than color in each direction.
        # For convenience, and consistent with Matlab, we
        # discard the last row and/or column of C if necessary
        # to meet this condition.  This is done if allmatch
        # is False.

        allmatch = kw.pop("allmatch", False)

        if len(args) == 1:
            C = args[0]
            numRows, numCols = C.shape
            if allmatch:
                X, Y = np.meshgrid(np.arange(numCols), np.arange(numRows))
            else:
                X, Y = np.meshgrid(np.arange(numCols + 1),
                                   np.arange(numRows + 1))
            return X, Y, C

        if len(args) == 3:
            X, Y, C = args
            numRows, numCols = C.shape
        else:
            raise TypeError(
                'Illegal arguments to %s; see help(%s)' % (funcname, funcname))

        Nx = X.shape[-1]
        Ny = Y.shape[0]
        if len(X.shape) != 2 or X.shape[0] == 1:
            x = X.reshape(1, Nx)
            X = x.repeat(Ny, axis=0)
        if len(Y.shape) != 2 or Y.shape[1] == 1:
            y = Y.reshape(Ny, 1)
            Y = y.repeat(Nx, axis=1)
        if X.shape != Y.shape:
            raise TypeError(
                'Incompatible X, Y inputs to %s; see help(%s)' % (
                funcname, funcname))
        if allmatch:
            if not (Nx == numCols and Ny == numRows):
                raise TypeError('Dimensions of C %s are incompatible with'
                                ' X (%d) and/or Y (%d); see help(%s)' % (
                                    C.shape, Nx, Ny, funcname))
        else:
            if not (numCols in (Nx, Nx - 1) and numRows in (Ny, Ny - 1)):
                raise TypeError('Dimensions of C %s are incompatible with'
                                ' X (%d) and/or Y (%d); see help(%s)' % (
                                    C.shape, Nx, Ny, funcname))
            C = C[:Ny - 1, :Nx - 1]
        return X, Y, C

    @docstring.dedent_interpd
    def pcolor(self, *args, **kwargs):
        """
        Create a pseudocolor plot of a 2-D array.

        .. note::

            pcolor can be very slow for large arrays; consider
            using the similar but much faster
            :func:`~matplotlib.pyplot.pcolormesh` instead.

        Call signatures::

          pcolor(C, **kwargs)
          pcolor(X, Y, C, **kwargs)

        *C* is the array of color values.

        *X* and *Y*, if given, specify the (*x*, *y*) coordinates of
        the colored quadrilaterals; the quadrilateral for C[i,j] has
        corners at::

          (X[i,   j],   Y[i,   j]),
          (X[i,   j+1], Y[i,   j+1]),
          (X[i+1, j],   Y[i+1, j]),
          (X[i+1, j+1], Y[i+1, j+1]).

        Ideally the dimensions of *X* and *Y* should be one greater
        than those of *C*; if the dimensions are the same, then the
        last row and column of *C* will be ignored.

        Note that the the column index corresponds to the
        *x*-coordinate, and the row index corresponds to *y*; for
        details, see the :ref:`Grid Orientation
        <axes-pcolor-grid-orientation>` section below.

        If either or both of *X* and *Y* are 1-D arrays or column vectors,
        they will be expanded as needed into the appropriate 2-D arrays,
        making a rectangular grid.

        *X*, *Y* and *C* may be masked arrays.  If either C[i, j], or one
        of the vertices surrounding C[i,j] (*X* or *Y* at [i, j], [i+1, j],
        [i, j+1],[i+1, j+1]) is masked, nothing is plotted.

        Keyword arguments:

          *cmap*: [ *None* | Colormap ]
            A :class:`matplotlib.colors.Colormap` instance. If *None*, use
            rc settings.

          *norm*: [ *None* | Normalize ]
            An :class:`matplotlib.colors.Normalize` instance is used
            to scale luminance data to 0,1. If *None*, defaults to
            :func:`normalize`.

          *vmin*/*vmax*: [ *None* | scalar ]
            *vmin* and *vmax* are used in conjunction with *norm* to
            normalize luminance data.  If either is *None*, it
            is autoscaled to the respective min or max
            of the color array *C*.  If not *None*, *vmin* or
            *vmax* passed in here override any pre-existing values
            supplied in the *norm* instance.

          *shading*: [ 'flat' | 'faceted' ]
            If 'faceted', a black grid is drawn around each rectangle; if
            'flat', edges are not drawn. Default is 'flat', contrary to
            MATLAB.

            This kwarg is deprecated; please use 'edgecolors' instead:
              * shading='flat' -- edgecolors='none'
              * shading='faceted  -- edgecolors='k'

          *edgecolors*: [ *None* | ``'none'`` | color | color sequence]
            If *None*, the rc setting is used by default.

            If ``'none'``, edges will not be visible.

            An mpl color or sequence of colors will set the edge color

          *alpha*: ``0 <= scalar <= 1``   or *None*
            the alpha blending value

          *snap*: bool
            Whether to snap the mesh to pixel boundaries.

        Return value is a :class:`matplotlib.collections.Collection`
        instance.

        .. _axes-pcolor-grid-orientation:

        The grid orientation follows the MATLAB convention: an
        array *C* with shape (*nrows*, *ncolumns*) is plotted with
        the column number as *X* and the row number as *Y*, increasing
        up; hence it is plotted the way the array would be printed,
        except that the *Y* axis is reversed.  That is, *C* is taken
        as *C*(*y*, *x*).

        Similarly for :func:`meshgrid`::

          x = np.arange(5)
          y = np.arange(3)
          X, Y = np.meshgrid(x, y)

        is equivalent to::

          X = array([[0, 1, 2, 3, 4],
                     [0, 1, 2, 3, 4],
                     [0, 1, 2, 3, 4]])

          Y = array([[0, 0, 0, 0, 0],
                     [1, 1, 1, 1, 1],
                     [2, 2, 2, 2, 2]])

        so if you have::

          C = rand(len(x), len(y))

        then you need to transpose C::

          pcolor(X, Y, C.T)

        or::

          pcolor(C.T)

        MATLAB :func:`pcolor` always discards the last row and column
        of *C*, but matplotlib displays the last row and column if *X* and
        *Y* are not specified, or if *X* and *Y* have one more row and
        column than *C*.

        kwargs can be used to control the
        :class:`~matplotlib.collections.PolyCollection` properties:

        %(PolyCollection)s

        .. note::

            The default *antialiaseds* is False if the default
            *edgecolors*="none" is used.  This eliminates artificial lines
            at patch boundaries, and works regardless of the value of
            alpha.  If *edgecolors* is not "none", then the default
            *antialiaseds* is taken from
            rcParams['patch.antialiased'], which defaults to *True*.
            Stroking the edges may be preferred if *alpha* is 1, but
            will cause artifacts otherwise.

        .. seealso::

            :func:`~matplotlib.pyplot.pcolormesh`
                For an explanation of the differences between
                pcolor and pcolormesh.
        """

        if not self._hold:
            self.cla()

        alpha = kwargs.pop('alpha', None)
        norm = kwargs.pop('norm', None)
        cmap = kwargs.pop('cmap', None)
        vmin = kwargs.pop('vmin', None)
        vmax = kwargs.pop('vmax', None)
        if 'shading' in kwargs:
            cbook.warn_deprecated(
                '1.2', name='shading', alternative='edgecolors',
                obj_type='option')
        shading = kwargs.pop('shading', 'flat')

        X, Y, C = self._pcolorargs('pcolor', *args, allmatch=False)
        Ny, Nx = X.shape

        # unit conversion allows e.g. datetime objects as axis values
        self._process_unit_info(xdata=X, ydata=Y, kwargs=kwargs)
        X = self.convert_xunits(X)
        Y = self.convert_yunits(Y)

        # convert to MA, if necessary.
        C = ma.asarray(C)
        X = ma.asarray(X)
        Y = ma.asarray(Y)

        mask = ma.getmaskarray(X) + ma.getmaskarray(Y)
        xymask = (mask[0:-1, 0:-1] + mask[1:, 1:] +
                  mask[0:-1, 1:] + mask[1:, 0:-1])
        # don't plot if C or any of the surrounding vertices are masked.
        mask = ma.getmaskarray(C) + xymask

        newaxis = np.newaxis
        compress = np.compress

        ravelmask = (mask == 0).ravel()
        X1 = compress(ravelmask, ma.filled(X[0:-1, 0:-1]).ravel())
        Y1 = compress(ravelmask, ma.filled(Y[0:-1, 0:-1]).ravel())
        X2 = compress(ravelmask, ma.filled(X[1:, 0:-1]).ravel())
        Y2 = compress(ravelmask, ma.filled(Y[1:, 0:-1]).ravel())
        X3 = compress(ravelmask, ma.filled(X[1:, 1:]).ravel())
        Y3 = compress(ravelmask, ma.filled(Y[1:, 1:]).ravel())
        X4 = compress(ravelmask, ma.filled(X[0:-1, 1:]).ravel())
        Y4 = compress(ravelmask, ma.filled(Y[0:-1, 1:]).ravel())
        npoly = len(X1)

        xy = np.concatenate((X1[:, newaxis], Y1[:, newaxis],
                             X2[:, newaxis], Y2[:, newaxis],
                             X3[:, newaxis], Y3[:, newaxis],
                             X4[:, newaxis], Y4[:, newaxis],
                             X1[:, newaxis], Y1[:, newaxis]),
                             axis=1)
        verts = xy.reshape((npoly, 5, 2))

        C = compress(ravelmask, ma.filled(C[0:Ny - 1, 0:Nx - 1]).ravel())

        linewidths = (0.25,)
        if 'linewidth' in kwargs:
            kwargs['linewidths'] = kwargs.pop('linewidth')
        kwargs.setdefault('linewidths', linewidths)

        if shading == 'faceted':
            edgecolors = 'k',
        else:
            edgecolors = 'none'

        if 'edgecolor' in kwargs:
            kwargs['edgecolors'] = kwargs.pop('edgecolor')
        ec = kwargs.setdefault('edgecolors', edgecolors)

        # aa setting will default via collections to patch.antialiased
        # unless the boundary is not stroked, in which case the
        # default will be False; with unstroked boundaries, aa
        # makes artifacts that are often disturbing.
        if 'antialiased' in kwargs:
            kwargs['antialiaseds'] = kwargs.pop('antialiased')
        if 'antialiaseds' not in kwargs and (is_string_like(ec) and
                ec.lower() == "none"):
            kwargs['antialiaseds'] = False

        kwargs.setdefault('snap', False)

        collection = mcoll.PolyCollection(verts, **kwargs)

        collection.set_alpha(alpha)
        collection.set_array(C)
        if norm is not None:
            assert(isinstance(norm, mcolors.Normalize))
        collection.set_cmap(cmap)
        collection.set_norm(norm)
        collection.set_clim(vmin, vmax)
        collection.autoscale_None()
        self.grid(False)

        x = X.compressed()
        y = Y.compressed()

        # Transform from native to data coordinates?
        t = collection._transform
        if (not isinstance(t, mtransforms.Transform)
            and hasattr(t, '_as_mpl_transform')):
            t = t._as_mpl_transform(self.axes)

        if t and any(t.contains_branch_seperately(self.transData)):
            trans_to_data = t - self.transData
            pts = np.vstack([x, y]).T.astype(np.float)
            transformed_pts = trans_to_data.transform(pts)
            x = transformed_pts[..., 0]
            y = transformed_pts[..., 1]

        minx = np.amin(x)
        maxx = np.amax(x)
        miny = np.amin(y)
        maxy = np.amax(y)

        corners = (minx, miny), (maxx, maxy)
        self.update_datalim(corners)
        self.autoscale_view()
        self.add_collection(collection, autolim=False)
        return collection

    @docstring.dedent_interpd
    def pcolormesh(self, *args, **kwargs):
        """
        Plot a quadrilateral mesh.

        Call signatures::

          pcolormesh(C)
          pcolormesh(X, Y, C)
          pcolormesh(C, **kwargs)

        Create a pseudocolor plot of a 2-D array.

        pcolormesh is similar to :func:`~matplotlib.pyplot.pcolor`,
        but uses a different mechanism and returns a different
        object; pcolor returns a
        :class:`~matplotlib.collections.PolyCollection` but pcolormesh
        returns a
        :class:`~matplotlib.collections.QuadMesh`.  It is much faster,
        so it is almost always preferred for large arrays.

        *C* may be a masked array, but *X* and *Y* may not.  Masked
        array support is implemented via *cmap* and *norm*; in
        contrast, :func:`~matplotlib.pyplot.pcolor` simply does not
        draw quadrilaterals with masked colors or vertices.

        Keyword arguments:

          *cmap*: [ *None* | Colormap ]
            A :class:`matplotlib.colors.Colormap` instance. If *None*, use
            rc settings.

          *norm*: [ *None* | Normalize ]
            A :class:`matplotlib.colors.Normalize` instance is used to
            scale luminance data to 0,1. If *None*, defaults to
            :func:`normalize`.

          *vmin*/*vmax*: [ *None* | scalar ]
            *vmin* and *vmax* are used in conjunction with *norm* to
            normalize luminance data.  If either is *None*, it
            is autoscaled to the respective min or max
            of the color array *C*.  If not *None*, *vmin* or
            *vmax* passed in here override any pre-existing values
            supplied in the *norm* instance.

          *shading*: [ 'flat' | 'gouraud' ]
            'flat' indicates a solid color for each quad.  When
            'gouraud', each quad will be Gouraud shaded.  When gouraud
            shading, edgecolors is ignored.

          *edgecolors*: [*None* | ``'None'`` | ``'face'`` | color |
                         color sequence]

            If *None*, the rc setting is used by default.

            If ``'None'``, edges will not be visible.

            If ``'face'``, edges will have the same color as the faces.

            An mpl color or sequence of colors will set the edge color

          *alpha*: ``0 <= scalar <= 1``  or *None*
            the alpha blending value

        Return value is a :class:`matplotlib.collections.QuadMesh`
        object.

        kwargs can be used to control the
        :class:`matplotlib.collections.QuadMesh` properties:

        %(QuadMesh)s

        .. seealso::

            :func:`~matplotlib.pyplot.pcolor`
                For an explanation of the grid orientation and the
                expansion of 1-D *X* and/or *Y* to 2-D arrays.
        """
        if not self._hold:
            self.cla()

        alpha = kwargs.pop('alpha', None)
        norm = kwargs.pop('norm', None)
        cmap = kwargs.pop('cmap', None)
        vmin = kwargs.pop('vmin', None)
        vmax = kwargs.pop('vmax', None)
        shading = kwargs.pop('shading', 'flat').lower()
        antialiased = kwargs.pop('antialiased', False)
        kwargs.setdefault('edgecolors', 'None')

        allmatch = (shading == 'gouraud')

        X, Y, C = self._pcolorargs('pcolormesh', *args, allmatch=allmatch)
        Ny, Nx = X.shape

        # convert to one dimensional arrays
        C = C.ravel()
        X = X.ravel()
        Y = Y.ravel()

        # unit conversion allows e.g. datetime objects as axis values
        self._process_unit_info(xdata=X, ydata=Y, kwargs=kwargs)
        X = self.convert_xunits(X)
        Y = self.convert_yunits(Y)

        coords = np.zeros(((Nx * Ny), 2), dtype=float)
        coords[:, 0] = X
        coords[:, 1] = Y

        collection = mcoll.QuadMesh(
            Nx - 1, Ny - 1, coords,
            antialiased=antialiased, shading=shading, **kwargs)
        collection.set_alpha(alpha)
        collection.set_array(C)
        if norm is not None:
            assert(isinstance(norm, mcolors.Normalize))
        collection.set_cmap(cmap)
        collection.set_norm(norm)
        collection.set_clim(vmin, vmax)
        collection.autoscale_None()

        self.grid(False)

        # Transform from native to data coordinates?
        t = collection._transform
        if (not isinstance(t, mtransforms.Transform)
            and hasattr(t, '_as_mpl_transform')):
            t = t._as_mpl_transform(self.axes)

        if t and any(t.contains_branch_seperately(self.transData)):
            trans_to_data = t - self.transData
            pts = np.vstack([X, Y]).T.astype(np.float)
            transformed_pts = trans_to_data.transform(pts)
            X = transformed_pts[..., 0]
            Y = transformed_pts[..., 1]

        minx = np.amin(X)
        maxx = np.amax(X)
        miny = np.amin(Y)
        maxy = np.amax(Y)

        corners = (minx, miny), (maxx, maxy)
        self.update_datalim(corners)
        self.autoscale_view()
        self.add_collection(collection, autolim=False)
        return collection

    @docstring.dedent_interpd
    def pcolorfast(self, *args, **kwargs):
        """
        pseudocolor plot of a 2-D array

        Experimental; this is a pcolor-type method that
        provides the fastest possible rendering with the Agg
        backend, and that can handle any quadrilateral grid.
        It supports only flat shading (no outlines), it lacks
        support for log scaling of the axes, and it does not
        have a pyplot wrapper.

        Call signatures::

          ax.pcolorfast(C, **kwargs)
          ax.pcolorfast(xr, yr, C, **kwargs)
          ax.pcolorfast(x, y, C, **kwargs)
          ax.pcolorfast(X, Y, C, **kwargs)

        C is the 2D array of color values corresponding to quadrilateral
        cells. Let (nr, nc) be its shape.  C may be a masked array.

        ``ax.pcolorfast(C, **kwargs)`` is equivalent to
        ``ax.pcolorfast([0,nc], [0,nr], C, **kwargs)``

        *xr*, *yr* specify the ranges of *x* and *y* corresponding to the
        rectangular region bounding *C*.  If::

            xr = [x0, x1]

        and::

            yr = [y0,y1]

        then *x* goes from *x0* to *x1* as the second index of *C* goes
        from 0 to *nc*, etc.  (*x0*, *y0*) is the outermost corner of
        cell (0,0), and (*x1*, *y1*) is the outermost corner of cell
        (*nr*-1, *nc*-1).  All cells are rectangles of the same size.
        This is the fastest version.

        *x*, *y* are 1D arrays of length *nc* +1 and *nr* +1, respectively,
        giving the x and y boundaries of the cells.  Hence the cells are
        rectangular but the grid may be nonuniform.  The speed is
        intermediate.  (The grid is checked, and if found to be
        uniform the fast version is used.)

        *X* and *Y* are 2D arrays with shape (*nr* +1, *nc* +1) that specify
        the (x,y) coordinates of the corners of the colored
        quadrilaterals; the quadrilateral for C[i,j] has corners at
        (X[i,j],Y[i,j]), (X[i,j+1],Y[i,j+1]), (X[i+1,j],Y[i+1,j]),
        (X[i+1,j+1],Y[i+1,j+1]).  The cells need not be rectangular.
        This is the most general, but the slowest to render.  It may
        produce faster and more compact output using ps, pdf, and
        svg backends, however.

        Note that the the column index corresponds to the x-coordinate,
        and the row index corresponds to y; for details, see
        the "Grid Orientation" section below.

        Optional keyword arguments:

          *cmap*: [ *None* | Colormap ]
            A :class:`matplotlib.colors.Colormap` instance from cm. If *None*,
            use rc settings.

          *norm*: [ *None* | Normalize ]
            A :class:`matplotlib.colors.Normalize` instance is used to scale
            luminance data to 0,1. If *None*, defaults to normalize()

          *vmin*/*vmax*: [ *None* | scalar ]
            *vmin* and *vmax* are used in conjunction with norm to normalize
            luminance data.  If either are *None*, the min and max
            of the color array *C* is used.  If you pass a norm instance,
            *vmin* and *vmax* will be *None*.

          *alpha*: ``0 <= scalar <= 1``  or *None*
            the alpha blending value

        Return value is an image if a regular or rectangular grid
        is specified, and a :class:`~matplotlib.collections.QuadMesh`
        collection in the general quadrilateral case.

        """

        if not self._hold:
            self.cla()

        alpha = kwargs.pop('alpha', None)
        norm = kwargs.pop('norm', None)
        cmap = kwargs.pop('cmap', None)
        vmin = kwargs.pop('vmin', None)
        vmax = kwargs.pop('vmax', None)
        if norm is not None:
            assert(isinstance(norm, mcolors.Normalize))

        C = args[-1]
        nr, nc = C.shape
        if len(args) == 1:
            style = "image"
            x = [0, nc]
            y = [0, nr]
        elif len(args) == 3:
            x, y = args[:2]
            x = np.asarray(x)
            y = np.asarray(y)
            if x.ndim == 1 and y.ndim == 1:
                if x.size == 2 and y.size == 2:
                    style = "image"
                else:
                    dx = np.diff(x)
                    dy = np.diff(y)
                    if (np.ptp(dx) < 0.01 * np.abs(dx.mean()) and
                        np.ptp(dy) < 0.01 * np.abs(dy.mean())):
                        style = "image"
                    else:
                        style = "pcolorimage"
            elif x.ndim == 2 and y.ndim == 2:
                style = "quadmesh"
            else:
                raise TypeError("arguments do not match valid signatures")
        else:
            raise TypeError("need 1 argument or 3 arguments")

        if style == "quadmesh":

            # convert to one dimensional arrays
            # This should also be moved to the QuadMesh class
            C = ma.ravel(C)  # data point in each cell is value
                             # at lower left corner
            X = x.ravel()
            Y = y.ravel()
            Nx = nc + 1
            Ny = nr + 1

            # The following needs to be cleaned up; the renderer
            # requires separate contiguous arrays for X and Y,
            # but the QuadMesh class requires the 2D array.
            coords = np.empty(((Nx * Ny), 2), np.float64)
            coords[:, 0] = X
            coords[:, 1] = Y

            # The QuadMesh class can also be changed to
            # handle relevant superclass kwargs; the initializer
            # should do much more than it does now.
            collection = mcoll.QuadMesh(nc, nr, coords, 0, edgecolors="None")
            collection.set_alpha(alpha)
            collection.set_array(C)
            collection.set_cmap(cmap)
            collection.set_norm(norm)
            self.add_collection(collection, autolim=False)
            xl, xr, yb, yt = X.min(), X.max(), Y.min(), Y.max()
            ret = collection

        else:
            # One of the image styles:
            xl, xr, yb, yt = x[0], x[-1], y[0], y[-1]
        if style == "image":

            im = mimage.AxesImage(self, cmap, norm,
                                        interpolation='nearest',
                                        origin='lower',
                                        extent=(xl, xr, yb, yt),
                                         **kwargs)
            im.set_data(C)
            im.set_alpha(alpha)
            self.add_image(im)
            ret = im

        if style == "pcolorimage":
            im = mimage.PcolorImage(self, x, y, C,
                                    cmap=cmap,
                                    norm=norm,
                                    alpha=alpha,
                                    **kwargs)
            self.add_image(im)
            ret = im

        if vmin is not None or vmax is not None:
            ret.set_clim(vmin, vmax)
        else:
            ret.autoscale_None()
        self.update_datalim(np.array([[xl, yb], [xr, yt]]))
        self.autoscale_view(tight=True)
        return ret

    def contour(self, *args, **kwargs):
        if not self._hold:
            self.cla()
        kwargs['filled'] = False
        return mcontour.QuadContourSet(self, *args, **kwargs)
    contour.__doc__ = mcontour.QuadContourSet.contour_doc

    def contourf(self, *args, **kwargs):
        if not self._hold:
            self.cla()
        kwargs['filled'] = True
        return mcontour.QuadContourSet(self, *args, **kwargs)
    contourf.__doc__ = mcontour.QuadContourSet.contour_doc

    def clabel(self, CS, *args, **kwargs):
        return CS.clabel(*args, **kwargs)
    clabel.__doc__ = mcontour.ContourSet.clabel.__doc__

    @docstring.dedent_interpd
    def table(self, **kwargs):
        """
        Add a table to the current axes.

        Call signature::

          table(cellText=None, cellColours=None,
                cellLoc='right', colWidths=None,
                rowLabels=None, rowColours=None, rowLoc='left',
                colLabels=None, colColours=None, colLoc='center',
                loc='bottom', bbox=None):

        Returns a :class:`matplotlib.table.Table` instance.  For finer
        grained control over tables, use the
        :class:`~matplotlib.table.Table` class and add it to the axes
        with :meth:`~matplotlib.axes.Axes.add_table`.

        Thanks to John Gill for providing the class and table.

        kwargs control the :class:`~matplotlib.table.Table`
        properties:

        %(Table)s
        """
        return mtable.table(self, **kwargs)

    #### Data analysis

    @docstring.dedent_interpd
    def hist(self, x, bins=10, range=None, normed=False, weights=None,
             cumulative=False, bottom=None, histtype='bar', align='mid',
             orientation='vertical', rwidth=None, log=False,
             color=None, label=None, stacked=False,
             **kwargs):
        """
        Plot a histogram.

        Compute and draw the histogram of *x*. The return value is a
        tuple (*n*, *bins*, *patches*) or ([*n0*, *n1*, ...], *bins*,
        [*patches0*, *patches1*,...]) if the input contains multiple
        data.

        Multiple data can be provided via *x* as a list of datasets
        of potentially different length ([*x0*, *x1*, ...]), or as
        a 2-D ndarray in which each column is a dataset.  Note that
        the ndarray form is transposed relative to the list form.

        Masked arrays are not supported at present.

        Parameters
        ----------
        x : (n,) array or sequence of (n,) arrays
            Input values, this takes either a single array or a sequency of
            arrays which are not required to be of the same length

        bins : integer or array_like, optional, default: 10
            If an integer is given, `bins + 1` bin edges are returned,
            consistently with :func:`numpy.histogram` for numpy version >=
            1.3.

            Unequally spaced bins are supported if `bins` is a sequence.

        range : tuple, optional, default: None
            The lower and upper range of the bins. Lower and upper outliers
            are ignored. If not provided, `range` is (x.min(), x.max()). Range
            has no effect if `bins` is a sequence.

            If `bins` is a sequence or `range` is specified, autoscaling
            is based on the specified bin range instead of the
            range of x.

        normed : boolean, optional, default: False
            If `True`, the first element of the return tuple will
            be the counts normalized to form a probability density, i.e.,
            ``n/(len(x)`dbin)``, i.e., the integral of the histogram will sum
            to 1. If *stacked* is also *True*, the sum of the histograms is
            normalized to 1.

        weights : array_like, shape (n, ), optional, default: None
            An array of weights, of the same shape as `x`.  Each value in `x`
            only contributes its associated weight towards the bin count
            (instead of 1).  If `normed` is True, the weights are normalized,
            so that the integral of the density over the range remains 1.

        cumulative : boolean, optional, default : False
            If `True`, then a histogram is computed where each bin gives the
            counts in that bin plus all bins for smaller values. The last bin
            gives the total number of datapoints.  If `normed` is also `True`
            then the histogram is normalized such that the last bin equals 1.
            If `cumulative` evaluates to less than 0 (e.g., -1), the direction
            of accumulation is reversed.  In this case, if `normed` is also
            `True`, then the histogram is normalized such that the first bin
            equals 1.

        bottom : array_like, scalar, or None, default: None
            Location of the bottom baseline of each bin.  If a scalar,
            the base line for each bin is shifted by the same amount.
            If an array, each bin is shifted independently and the length
            of bottom must match the number of bins.  If None, defaults to 0.

        histtype : ['bar' | 'barstacked' | 'step' | 'stepfilled'], optional
            The type of histogram to draw.

            - 'bar' is a traditional bar-type histogram.  If multiple data
              are given the bars are aranged side by side.

            - 'barstacked' is a bar-type histogram where multiple
              data are stacked on top of each other.

            - 'step' generates a lineplot that is by default
              unfilled.

            - 'stepfilled' generates a lineplot that is by default
              filled.

        align : ['left' | 'mid' | 'right'], optional, default: 'mid'
            Controls how the histogram is plotted.

                - 'left': bars are centered on the left bin edges.

                - 'mid': bars are centered between the bin edges.

                - 'right': bars are centered on the right bin edges.

        orientation : ['horizontal' | 'vertical'], optional
            If 'horizontal', `~matplotlib.pyplot.barh` will be used for
            bar-type histograms and the *bottom* kwarg will be the left edges.

        rwidth : scalar, optional, default: None
            The relative width of the bars as a fraction of the bin width.  If
            `None`, automatically compute the width. Ignored if `histtype` =
            'step' or 'stepfilled'.

        log : boolean, optional, default : False
            If `True`, the histogram axis will be set to a log scale. If `log`
            is `True` and `x` is a 1D array, empty bins will be filtered out
            and only the non-empty (`n`, `bins`, `patches`) will be returned.

        color : color or array_like of colors, optional, default: None
            Color spec or sequence of color specs, one per dataset.  Default
            (`None`) uses the standard line color sequence.

        label : string, optional, default: ''
            String, or sequence of strings to match multiple datasets.  Bar
            charts yield multiple patches per dataset, but only the first gets
            the label, so that the legend command will work as expected.

        stacked : boolean, optional, default : False
            If `True`, multiple data are stacked on top of each other If
            `False` multiple data are aranged side by side if histtype is
            'bar' or on top of each other if histtype is 'step'

        Returns
        -------
        n : array or list of arrays
            The values of the histogram bins. See **normed** and **weights**
            for a description of the possible semantics. If input **x** is an
            array, then this is an array of length **nbins**. If input is a
            sequence arrays ``[data1, data2,..]``, then this is a list of
            arrays with the values of the histograms for each of the arrays
            in the same order.

        bins : array
            The edges of the bins. Length nbins + 1 (nbins left edges and right
            edge of last bin).  Always a single array even when multiple data
            sets are passed in.

        patches : list or list of lists
            Silent list of individual patches used to create the histogram
            or list of such list if multiple input datasets.

        Other Parameters
        ----------------
        kwargs : `~matplotlib.patches.Patch` properties

        See also
        --------
        hist2d : 2D histograms

        Notes
        -----
        Until numpy release 1.5, the underlying numpy histogram function was
        incorrect with `normed`=`True` if bin sizes were unequal.  MPL
        inherited that error.  It is now corrected within MPL when using
        earlier numpy versions.

        Examples
        --------
        .. plot:: mpl_examples/statistics/histogram_demo_features.py

        """
        if not self._hold:
            self.cla()

        # xrange becomes range after 2to3
        bin_range = range
        range = __builtins__["range"]

        # NOTE: the range keyword overwrites the built-in func range !!!
        #       needs to be fixed in numpy                           !!!

        # Validate string inputs here so we don't have to clutter
        # subsequent code.
        if histtype not in ['bar', 'barstacked', 'step', 'stepfilled']:
            raise ValueError("histtype %s is not recognized" % histtype)

        if align not in ['left', 'mid', 'right']:
            raise ValueError("align kwarg %s is not recognized" % align)

        if orientation not in ['horizontal', 'vertical']:
            raise ValueError(
                "orientation kwarg %s is not recognized" % orientation)

        if histtype == 'barstacked' and not stacked:
            stacked = True

        # Check whether bins or range are given explicitly.
        binsgiven = (cbook.iterable(bins) or bin_range is not None)

        # basic input validation
        flat = np.ravel(x)
        if len(flat) == 0:
            raise ValueError("x must have at least one data point")
        elif len(flat) == 1 and not binsgiven:
            raise ValueError(
                "x has only one data point. bins or range kwarg must be given")

        # Massage 'x' for processing.
        # NOTE: Be sure any changes here is also done below to 'weights'
        if isinstance(x, np.ndarray) or not iterable(x[0]):
            # TODO: support masked arrays;
            x = np.asarray(x)
            if x.ndim == 2:
                x = x.T  # 2-D input with columns as datasets; switch to rows
            elif x.ndim == 1:
                x = x.reshape(1, x.shape[0])  # new view, single row
            else:
                raise ValueError("x must be 1D or 2D")
            if x.shape[1] < x.shape[0]:
                warnings.warn(
                    '2D hist input should be nsamples x nvariables;\n '
                    'this looks transposed (shape is %d x %d)' % x.shape[::-1])
        else:
            # multiple hist with data of different length
            x = [np.asarray(xi) for xi in x]

        nx = len(x)  # number of datasets

        if color is None:
            color = [six.next(self._get_lines.color_cycle)
                     for i in xrange(nx)]
        else:
            color = mcolors.colorConverter.to_rgba_array(color)
            if len(color) != nx:
                raise ValueError("color kwarg must have one color per dataset")

        # We need to do to 'weights' what was done to 'x'
        if weights is not None:
            if isinstance(weights, np.ndarray) or not iterable(weights[0]):
                w = np.array(weights)
                if w.ndim == 2:
                    w = w.T
                elif w.ndim == 1:
                    w.shape = (1, w.shape[0])
                else:
                    raise ValueError("weights must be 1D or 2D")
            else:
                w = [np.asarray(wi) for wi in weights]

            if len(w) != nx:
                raise ValueError('weights should have the same shape as x')
            for i in xrange(nx):
                if len(w[i]) != len(x[i]):
                    raise ValueError(
                        'weights should have the same shape as x')
        else:
            w = [None]*nx

        # Save the datalimits for the same reason:
        _saved_bounds = self.dataLim.bounds

        # If bins are not specified either explicitly or via range,
        # we need to figure out the range required for all datasets,
        # and supply that to np.histogram.
        if not binsgiven:
            xmin = np.inf
            xmax = -np.inf
            for xi in x:
                if len(xi) > 0:
                    xmin = min(xmin, xi.min())
                    xmax = max(xmax, xi.max())
            bin_range = (xmin, xmax)

        #hist_kwargs = dict(range=range, normed=bool(normed))
        # We will handle the normed kwarg within mpl until we
        # get to the point of requiring numpy >= 1.5.
        hist_kwargs = dict(range=bin_range)

        n = []
        mlast = None
        for i in xrange(nx):
            # this will automatically overwrite bins,
            # so that each histogram uses the same bins
            m, bins = np.histogram(x[i], bins, weights=w[i], **hist_kwargs)
            m = m.astype(float)  # causes problems later if it's an int
            if mlast is None:
                mlast = np.zeros(len(bins)-1, m.dtype)
            if normed and not stacked:
                db = np.diff(bins)
                m = (m.astype(float) / db) / m.sum()
            if stacked:
                if mlast is None:
                    mlast = np.zeros(len(bins)-1, m.dtype)
                m += mlast
                mlast[:] = m
            n.append(m)

        if stacked and normed:
            db = np.diff(bins)
            for m in n:
                m[:] = (m.astype(float) / db) / n[-1].sum()
        if cumulative:
            slc = slice(None)
            if cbook.is_numlike(cumulative) and cumulative < 0:
                slc = slice(None, None, -1)

            if normed:
                n = [(m * np.diff(bins))[slc].cumsum()[slc] for m in n]
            else:
                n = [m[slc].cumsum()[slc] for m in n]

        patches = []

        if histtype.startswith('bar'):
            # Save autoscale state for later restoration; turn autoscaling
            # off so we can do it all a single time at the end, instead
            # of having it done by bar or fill and then having to be redone.
            _saved_autoscalex = self.get_autoscalex_on()
            _saved_autoscaley = self.get_autoscaley_on()
            self.set_autoscalex_on(False)
            self.set_autoscaley_on(False)

            totwidth = np.diff(bins)

            if rwidth is not None:
                dr = min(1.0, max(0.0, rwidth))
            elif len(n) > 1:
                dr = 0.8
            else:
                dr = 1.0

            if histtype == 'bar' and not stacked:
                width = dr*totwidth/nx
                dw = width

                if nx > 1:
                    boffset = -0.5*dr*totwidth*(1.0-1.0/nx)
                else:
                    boffset = 0.0
                stacked = False
            elif histtype == 'barstacked' or stacked:
                width = dr*totwidth
                boffset, dw = 0.0, 0.0

            if align == 'mid' or align == 'edge':
                boffset += 0.5*totwidth
            elif align == 'right':
                boffset += totwidth

            if orientation == 'horizontal':
                _barfunc = self.barh
                bottom_kwarg = 'left'
            else:  # orientation == 'vertical'
                _barfunc = self.bar
                bottom_kwarg = 'bottom'

            for m, c in zip(n, color):
                if bottom is None:
                    bottom = np.zeros(len(m), np.float)
                if stacked:
                    height = m - bottom
                else:
                    height = m
                patch = _barfunc(bins[:-1]+boffset, height, width,
                                 align='center', log=log,
                                 color=c, **{bottom_kwarg: bottom})
                patches.append(patch)
                if stacked:
                    bottom[:] = m
                boffset += dw

            self.set_autoscalex_on(_saved_autoscalex)
            self.set_autoscaley_on(_saved_autoscaley)
            self.autoscale_view()

        elif histtype.startswith('step'):
            # these define the perimeter of the polygon
            x = np.zeros(4 * len(bins) - 3, np.float)
            y = np.zeros(4 * len(bins) - 3, np.float)

            x[0:2*len(bins)-1:2], x[1:2*len(bins)-1:2] = bins, bins[:-1]
            x[2*len(bins)-1:] = x[1:2*len(bins)-1][::-1]

            if bottom is None:
                bottom = np.zeros(len(bins)-1, np.float)

            y[1:2*len(bins)-1:2], y[2:2*len(bins):2] = bottom, bottom
            y[2*len(bins)-1:] = y[1:2*len(bins)-1][::-1]

            if log:
                if orientation == 'horizontal':
                    self.set_xscale('log', nonposx='clip')
                    logbase = self.xaxis._scale.base
                else:  # orientation == 'vertical'
                    self.set_yscale('log', nonposy='clip')
                    logbase = self.yaxis._scale.base

                # Setting a minimum of 0 results in problems for log plots
                if normed or weights is not None:
                    # For normed data, set to log base * minimum data value
                    # (gives 1 full tick-label unit for the lowest filled bin)
                    ndata = np.array(n)
                    minimum = (np.min(ndata[ndata > 0])) / logbase
                else:
                    # For non-normed data, set the min to log base,
                    # again so that there is 1 full tick-label unit
                    # for the lowest bin
                    minimum = 1.0 / logbase

                y[0], y[-1] = minimum, minimum
            else:
                minimum = np.min(bins)

            if align == 'left' or align == 'center':
                x -= 0.5*(bins[1]-bins[0])
            elif align == 'right':
                x += 0.5*(bins[1]-bins[0])

            # If fill kwarg is set, it will be passed to the patch collection,
            # overriding this
            fill = (histtype == 'stepfilled')

            xvals, yvals = [], []
            for m in n:
                if stacked:
                    # starting point for drawing polygon
                    y[0] = y[1]
                    # top of the previous polygon becomes the bottom
                    y[2*len(bins)-1:] = y[1:2*len(bins)-1][::-1]
                # set the top of this polygon
                y[1:2*len(bins)-1:2], y[2:2*len(bins):2] = (m + bottom,
                                                            m + bottom)
                if log:
                    y[y < minimum] = minimum
                if orientation == 'horizontal':
                    xvals.append(y.copy())
                    yvals.append(x.copy())
                else:
                    xvals.append(x.copy())
                    yvals.append(y.copy())

            if fill:
                # add patches in reverse order so that when stacking,
                # items lower in the stack are plottted on top of
                # items higher in the stack
                for x, y, c in reversed(list(zip(xvals, yvals, color))):
                    patches.append(self.fill(
                        x, y,
                        closed=True,
                        facecolor=c))
            else:
                for x, y, c in reversed(list(zip(xvals, yvals, color))):
                    split = 2 * len(bins)
                    patches.append(self.fill(
                        x[:split], y[:split],
                        closed=False, edgecolor=c,
                        fill=False))

            # we return patches, so put it back in the expected order
            patches.reverse()

            # adopted from adjust_x/ylim part of the bar method
            if orientation == 'horizontal':
                xmin0 = max(_saved_bounds[0]*0.9, minimum)
                xmax = self.dataLim.intervalx[1]
                for m in n:
                    if np.sum(m) > 0:  # make sure there are counts
                        xmin = np.amin(m[m != 0])
                        # filter out the 0 height bins
                xmin = max(xmin*0.9, minimum)
                xmin = min(xmin0, xmin)
                self.dataLim.intervalx = (xmin, xmax)
            elif orientation == 'vertical':
                ymin0 = max(_saved_bounds[1]*0.9, minimum)
                ymax = self.dataLim.intervaly[1]
                for m in n:
                    if np.sum(m) > 0:  # make sure there are counts
                        ymin = np.amin(m[m != 0])
                        # filter out the 0 height bins
                ymin = max(ymin*0.9, minimum)
                ymin = min(ymin0, ymin)
                self.dataLim.intervaly = (ymin, ymax)

        if label is None:
            labels = [None]
        elif is_string_like(label):
            labels = [label]
        elif is_sequence_of_strings(label):
            labels = list(label)
        else:
            raise ValueError(
                'invalid label: must be string or sequence of strings')

        if len(labels) < nx:
            labels += [None] * (nx - len(labels))

        for (patch, lbl) in zip(patches, labels):
            if patch:
                p = patch[0]
                p.update(kwargs)
                if lbl is not None:
                    p.set_label(lbl)

                p.set_snap(False)

                for p in patch[1:]:
                    p.update(kwargs)
                    p.set_label('_nolegend_')

        if binsgiven:
            if orientation == 'vertical':
                self.update_datalim(
                    [(bins[0], 0), (bins[-1], 0)], updatey=False)
            else:
                self.update_datalim(
                    [(0, bins[0]), (0, bins[-1])], updatex=False)

        if nx == 1:
            return n[0], bins, cbook.silent_list('Patch', patches[0])
        else:
            return n, bins, cbook.silent_list('Lists of Patches', patches)

    @docstring.dedent_interpd
    def hist2d(self, x, y, bins=10, range=None, normed=False, weights=None,
               cmin=None, cmax=None, **kwargs):
        """
        Make a 2D histogram plot.

        Parameters
        ----------
        x, y: array_like, shape (n, )
            Input values

        bins: [None | int | [int, int] | array_like | [array, array]]

            The bin specification:

                - If int, the number of bins for the two dimensions
                  (nx=ny=bins).

                - If [int, int], the number of bins in each dimension
                  (nx, ny = bins).

                - If array_like, the bin edges for the two dimensions
                  (x_edges=y_edges=bins).

                - If [array, array], the bin edges in each dimension
                  (x_edges, y_edges = bins).

            The default value is 10.

        range : array_like shape(2, 2), optional, default: None
             The leftmost and rightmost edges of the bins along each dimension
             (if not specified explicitly in the bins parameters): [[xmin,
             xmax], [ymin, ymax]]. All values outside of this range will be
             considered outliers and not tallied in the histogram.

        normed : boolean, optional, default: False
             Normalize histogram.

        weights : array_like, shape (n, ), optional, default: None
            An array of values w_i weighing each sample (x_i, y_i).

        cmin : scalar, optional, default: None
             All bins that has count less than cmin will not be displayed and
             these count values in the return value count histogram will also
             be set to nan upon return

        cmax : scalar, optional, default: None
             All bins that has count more than cmax will not be displayed (set
             to none before passing to imshow) and these count values in the
             return value count histogram will also be set to nan upon return

        Returns
        -------
        The return value is ``(counts, xedges, yedges, Image)``.

        Other parameters
        -----------------
        kwargs : :meth:`pcolorfast` properties.

        See also
        --------
        hist : 1D histogram

        Notes
        -----
        Rendering the histogram with a logarithmic color scale is
        accomplished by passing a :class:`colors.LogNorm` instance to
        the *norm* keyword argument. Likewise, power-law normalization
        (similar in effect to gamma correction) can be accomplished with
        :class:`colors.PowerNorm`.

        Examples
        --------
        .. plot:: mpl_examples/pylab_examples/hist2d_demo.py
        """

        # xrange becomes range after 2to3
        bin_range = range
        range = __builtins__["range"]
        h, xedges, yedges = np.histogram2d(x, y, bins=bins, range=bin_range,
                                           normed=normed, weights=weights)

        if cmin is not None:
            h[h < cmin] = None
        if cmax is not None:
            h[h > cmax] = None

        pc = self.pcolorfast(xedges, yedges, h.T, **kwargs)
        self.set_xlim(xedges[0], xedges[-1])
        self.set_ylim(yedges[0], yedges[-1])

        return h, xedges, yedges, pc

    @docstring.dedent_interpd
    def psd(self, x, NFFT=None, Fs=None, Fc=None, detrend=None,
            window=None, noverlap=None, pad_to=None,
            sides=None, scale_by_freq=None, return_line=None, **kwargs):
        """
        Plot the power spectral density.

        Call signature::

          psd(x, NFFT=256, Fs=2, Fc=0, detrend=mlab.detrend_none,
              window=mlab.window_hanning, noverlap=0, pad_to=None,
              sides='default', scale_by_freq=None, return_line=None, **kwargs)

        The power spectral density :math:`P_{xx}` by Welch's average
        periodogram method.  The vector *x* is divided into *NFFT* length
        segments.  Each segment is detrended by function *detrend* and
        windowed by function *window*.  *noverlap* gives the length of
        the overlap between segments.  The :math:`|\mathrm{fft}(i)|^2`
        of each segment :math:`i` are averaged to compute :math:`P_{xx}`,
        with a scaling to correct for power loss due to windowing.

        If len(*x*) < *NFFT*, it will be zero padded to *NFFT*.

          *x*: 1-D array or sequence
            Array or sequence containing the data

        %(Spectral)s

        %(PSD)s

          *noverlap*: integer
            The number of points of overlap between segments.
            The default value is 0 (no overlap).

          *Fc*: integer
            The center frequency of *x* (defaults to 0), which offsets
            the x extents of the plot to reflect the frequency range used
            when a signal is acquired and then filtered and downsampled to
            baseband.

          *return_line*: bool
            Whether to include the line object plotted in the returned values.
            Default is False.

        If *return_line* is False, returns the tuple (*Pxx*, *freqs*).
        If *return_line* is True, returns the tuple (*Pxx*, *freqs*. *line*):

          *Pxx*: 1-D array
            The values for the power spectrum `P_{xx}` before scaling
            (real valued)

          *freqs*: 1-D array
            The frequencies corresponding to the elements in *Pxx*

          *line*: a :class:`~matplotlib.lines.Line2D` instance
            The line created by this function.
            Only returend if *return_line* is True.

        For plotting, the power is plotted as
        :math:`10\log_{10}(P_{xx})` for decibels, though *Pxx* itself
        is returned.

        References:
          Bendat & Piersol -- Random Data: Analysis and Measurement
          Procedures, John Wiley & Sons (1986)

        kwargs control the :class:`~matplotlib.lines.Line2D` properties:

        %(Line2D)s

        **Example:**

        .. plot:: mpl_examples/pylab_examples/psd_demo.py

        .. seealso::

            :func:`specgram`
                :func:`specgram` differs in the default overlap; in not
                returning the mean of the segment periodograms; in  returning
                the times of the segments; and in plotting a colormap instead
                of a line.

            :func:`magnitude_spectrum`
                :func:`magnitude_spectrum` plots the magnitude spectrum.

            :func:`csd`
                :func:`csd` plots the spectral density between two signals.
        """
        if not self._hold:
            self.cla()

        if Fc is None:
            Fc = 0

        pxx, freqs = mlab.psd(x=x, NFFT=NFFT, Fs=Fs, detrend=detrend,
                              window=window, noverlap=noverlap, pad_to=pad_to,
                              sides=sides, scale_by_freq=scale_by_freq)
        pxx.shape = len(freqs),
        freqs += Fc

        if scale_by_freq in (None, True):
            psd_units = 'dB/Hz'
        else:
            psd_units = 'dB'

        line = self.plot(freqs, 10 * np.log10(pxx), **kwargs)
        self.set_xlabel('Frequency')
        self.set_ylabel('Power Spectral Density (%s)' % psd_units)
        self.grid(True)
        vmin, vmax = self.viewLim.intervaly
        intv = vmax - vmin
        logi = int(np.log10(intv))
        if logi == 0:
            logi = .1
        step = 10 * logi
        #print vmin, vmax, step, intv, math.floor(vmin), math.ceil(vmax)+1
        ticks = np.arange(math.floor(vmin), math.ceil(vmax) + 1, step)
        self.set_yticks(ticks)

        if return_line is None or not return_line:
            return pxx, freqs
        else:
            return pxx, freqs, line

    @docstring.dedent_interpd
    def csd(self, x, y, NFFT=None, Fs=None, Fc=None, detrend=None,
            window=None, noverlap=None, pad_to=None,
            sides=None, scale_by_freq=None, return_line=None, **kwargs):
        """
        Plot the cross-spectral density.

        Call signature::

          csd(x, y, NFFT=256, Fs=2, Fc=0, detrend=mlab.detrend_none,
              window=mlab.window_hanning, noverlap=0, pad_to=None,
              sides='default', scale_by_freq=None, return_line=None, **kwargs)

        The cross spectral density :math:`P_{xy}` by Welch's average
        periodogram method.  The vectors *x* and *y* are divided into
        *NFFT* length segments.  Each segment is detrended by function
        *detrend* and windowed by function *window*.  *noverlap* gives
        the length of the overlap between segments.  The product of
        the direct FFTs of *x* and *y* are averaged over each segment
        to compute :math:`P_{xy}`, with a scaling to correct for power
        loss due to windowing.

        If len(*x*) < *NFFT* or len(*y*) < *NFFT*, they will be zero
        padded to *NFFT*.

          *x*, *y*: 1-D arrays or sequences
            Arrays or sequences containing the data

        %(Spectral)s

        %(PSD)s

          *noverlap*: integer
            The number of points of overlap between segments.
            The default value is 0 (no overlap).

          *Fc*: integer
            The center frequency of *x* (defaults to 0), which offsets
            the x extents of the plot to reflect the frequency range used
            when a signal is acquired and then filtered and downsampled to
            baseband.

          *return_line*: bool
            Whether to include the line object plotted in the returned values.
            Default is False.

        If *return_line* is False, returns the tuple (*Pxy*, *freqs*).
        If *return_line* is True, returns the tuple (*Pxy*, *freqs*. *line*):

          *Pxy*: 1-D array
            The values for the cross spectrum `P_{xy}` before scaling
            (complex valued)

          *freqs*: 1-D array
            The frequencies corresponding to the elements in *Pxy*

          *line*: a :class:`~matplotlib.lines.Line2D` instance
            The line created by this function.
            Only returend if *return_line* is True.

        For plotting, the power is plotted as
        :math:`10\log_{10}(P_{xy})` for decibels, though `P_{xy}` itself
        is returned.

        References:
          Bendat & Piersol -- Random Data: Analysis and Measurement
          Procedures, John Wiley & Sons (1986)

        kwargs control the Line2D properties:

        %(Line2D)s

        **Example:**

        .. plot:: mpl_examples/pylab_examples/csd_demo.py

        .. seealso::

            :func:`psd`
                :func:`psd` is the equivalent to setting y=x.
        """
        if not self._hold:
            self.cla()

        if Fc is None:
            Fc = 0

        pxy, freqs = mlab.csd(x=x, y=y, NFFT=NFFT, Fs=Fs, detrend=detrend,
                              window=window, noverlap=noverlap, pad_to=pad_to,
                              sides=sides, scale_by_freq=scale_by_freq)
        pxy.shape = len(freqs),
        # pxy is complex
        freqs += Fc

        line = self.plot(freqs, 10 * np.log10(np.absolute(pxy)), **kwargs)
        self.set_xlabel('Frequency')
        self.set_ylabel('Cross Spectrum Magnitude (dB)')
        self.grid(True)
        vmin, vmax = self.viewLim.intervaly

        intv = vmax - vmin
        step = 10 * int(np.log10(intv))

        ticks = np.arange(math.floor(vmin), math.ceil(vmax) + 1, step)
        self.set_yticks(ticks)

        if return_line is None or not return_line:
            return pxy, freqs
        else:
            return pxy, freqs, line

    @docstring.dedent_interpd
    def magnitude_spectrum(self, x, Fs=None, Fc=None, window=None,
                           pad_to=None, sides=None, scale=None,
                           **kwargs):
        """
        Plot the magnitude spectrum.

        Call signature::

          magnitude_spectrum(x, Fs=2, Fc=0,  window=mlab.window_hanning,
                             pad_to=None, sides='default', **kwargs)

        Compute the magnitude spectrum of *x*.  Data is padded to a
        length of *pad_to* and the windowing function *window* is applied to
        the signal.

          *x*: 1-D array or sequence
            Array or sequence containing the data

        %(Spectral)s

        %(Single_Spectrum)s

          *scale*: [ 'default' | 'linear' | 'dB' ]
            The scaling of the values in the *spec*.  'linear' is no scaling.
            'dB' returns the values in dB scale.  When *mode* is 'density',
            this is dB power (10 * log10).  Otherwise this is dB amplitude
            (20 * log10). 'default' is 'linear'.

          *Fc*: integer
            The center frequency of *x* (defaults to 0), which offsets
            the x extents of the plot to reflect the frequency range used
            when a signal is acquired and then filtered and downsampled to
            baseband.

        Returns the tuple (*spectrum*, *freqs*, *line*):

          *spectrum*: 1-D array
            The values for the magnitude spectrum before scaling (real valued)

          *freqs*: 1-D array
            The frequencies corresponding to the elements in *spectrum*

          *line*: a :class:`~matplotlib.lines.Line2D` instance
            The line created by this function

        kwargs control the :class:`~matplotlib.lines.Line2D` properties:

        %(Line2D)s

        **Example:**

        .. plot:: mpl_examples/pylab_examples/spectrum_demo.py

        .. seealso::

            :func:`psd`
                :func:`psd` plots the power spectral density.`.

            :func:`angle_spectrum`
                :func:`angle_spectrum` plots the angles of the corresponding
                frequencies.

            :func:`phase_spectrum`
                :func:`phase_spectrum` plots the phase (unwrapped angle) of the
                corresponding frequencies.

            :func:`specgram`
                :func:`specgram` can plot the magnitude spectrum of segments
                within the signal in a colormap.
        """
        if not self._hold:
            self.cla()

        if Fc is None:
            Fc = 0

        if scale is None or scale == 'default':
            scale = 'linear'

        spec, freqs = mlab.magnitude_spectrum(x=x, Fs=Fs, window=window,
                                              pad_to=pad_to, sides=sides)
        freqs += Fc

        if scale == 'linear':
            Z = spec
            yunits = 'energy'
        elif scale == 'dB':
            Z = 20. * np.log10(spec)
            yunits = 'dB'
        else:
            raise ValueError('Unknown scale %s', scale)

        lines = self.plot(freqs, Z, **kwargs)
        self.set_xlabel('Frequency')
        self.set_ylabel('Magnitude (%s)' % yunits)

        return spec, freqs, lines[0]

    @docstring.dedent_interpd
    def angle_spectrum(self, x, Fs=None, Fc=None, window=None,
                       pad_to=None, sides=None, **kwargs):
        """
        Plot the angle spectrum.

        Call signature::

          angle_spectrum(x, Fs=2, Fc=0,  window=mlab.window_hanning,
                         pad_to=None, sides='default', **kwargs)

        Compute the angle spectrum (wrapped phase spectrum) of *x*.
        Data is padded to a length of *pad_to* and the windowing function
        *window* is applied to the signal.

          *x*: 1-D array or sequence
            Array or sequence containing the data

        %(Spectral)s

        %(Single_Spectrum)s

          *Fc*: integer
            The center frequency of *x* (defaults to 0), which offsets
            the x extents of the plot to reflect the frequency range used
            when a signal is acquired and then filtered and downsampled to
            baseband.

        Returns the tuple (*spectrum*, *freqs*, *line*):

          *spectrum*: 1-D array
            The values for the angle spectrum in radians (real valued)

          *freqs*: 1-D array
            The frequencies corresponding to the elements in *spectrum*

          *line*: a :class:`~matplotlib.lines.Line2D` instance
            The line created by this function

        kwargs control the :class:`~matplotlib.lines.Line2D` properties:

        %(Line2D)s

        **Example:**

        .. plot:: mpl_examples/pylab_examples/spectrum_demo.py

        .. seealso::

            :func:`magnitude_spectrum`
                :func:`angle_spectrum` plots the magnitudes of the
                corresponding frequencies.

            :func:`phase_spectrum`
                :func:`phase_spectrum` plots the unwrapped version of this
                function.

            :func:`specgram`
                :func:`specgram` can plot the angle spectrum of segments
                within the signal in a colormap.
        """
        if not self._hold:
            self.cla()

        if Fc is None:
            Fc = 0

        spec, freqs = mlab.angle_spectrum(x=x, Fs=Fs, window=window,
                                          pad_to=pad_to, sides=sides)
        freqs += Fc

        lines = self.plot(freqs, spec, **kwargs)
        self.set_xlabel('Frequency')
        self.set_ylabel('Angle (radians)')

        return spec, freqs, lines[0]

    @docstring.dedent_interpd
    def phase_spectrum(self, x, Fs=None, Fc=None, window=None,
                       pad_to=None, sides=None, **kwargs):
        """
        Plot the phase spectrum.

        Call signature::

          phase_spectrum(x, Fs=2, Fc=0,  window=mlab.window_hanning,
                         pad_to=None, sides='default', **kwargs)

        Compute the phase spectrum (unwrapped angle spectrum) of *x*.
        Data is padded to a length of *pad_to* and the windowing function
        *window* is applied to the signal.

          *x*: 1-D array or sequence
            Array or sequence containing the data

        %(Spectral)s

        %(Single_Spectrum)s

          *Fc*: integer
            The center frequency of *x* (defaults to 0), which offsets
            the x extents of the plot to reflect the frequency range used
            when a signal is acquired and then filtered and downsampled to
            baseband.

        Returns the tuple (*spectrum*, *freqs*, *line*):

          *spectrum*: 1-D array
            The values for the phase spectrum in radians (real valued)

          *freqs*: 1-D array
            The frequencies corresponding to the elements in *spectrum*

          *line*: a :class:`~matplotlib.lines.Line2D` instance
            The line created by this function

        kwargs control the :class:`~matplotlib.lines.Line2D` properties:

        %(Line2D)s

        **Example:**

        .. plot:: mpl_examples/pylab_examples/spectrum_demo.py

        .. seealso::

            :func:`magnitude_spectrum`
                :func:`magnitude_spectrum` plots the magnitudes of the
                corresponding frequencies.

            :func:`angle_spectrum`
                :func:`angle_spectrum` plots the wrapped version of this
                function.

            :func:`specgram`
                :func:`specgram` can plot the phase spectrum of segments
                within the signal in a colormap.
        """
        if not self._hold:
            self.cla()

        if Fc is None:
            Fc = 0

        spec, freqs = mlab.phase_spectrum(x=x, Fs=Fs, window=window,
                                          pad_to=pad_to, sides=sides)
        freqs += Fc

        lines = self.plot(freqs, spec, **kwargs)
        self.set_xlabel('Frequency')
        self.set_ylabel('Phase (radians)')

        return spec, freqs, lines[0]

    @docstring.dedent_interpd
    def cohere(self, x, y, NFFT=256, Fs=2, Fc=0, detrend=mlab.detrend_none,
               window=mlab.window_hanning, noverlap=0, pad_to=None,
               sides='default', scale_by_freq=None, **kwargs):
        """
        Plot the coherence between *x* and *y*.

        Call signature::

          cohere(x, y, NFFT=256, Fs=2, Fc=0, detrend = mlab.detrend_none,
                 window = mlab.window_hanning, noverlap=0, pad_to=None,
                 sides='default', scale_by_freq=None, **kwargs)

        Plot the coherence between *x* and *y*.  Coherence is the
        normalized cross spectral density:

        .. math::

          C_{xy} = \\frac{|P_{xy}|^2}{P_{xx}P_{yy}}

        %(Spectral)s

        %(PSD)s

          *noverlap*: integer
            The number of points of overlap between blocks.  The
            default value is 0 (no overlap).

          *Fc*: integer
            The center frequency of *x* (defaults to 0), which offsets
            the x extents of the plot to reflect the frequency range used
            when a signal is acquired and then filtered and downsampled to
            baseband.

        The return value is a tuple (*Cxy*, *f*), where *f* are the
        frequencies of the coherence vector.

        kwargs are applied to the lines.

        References:

          * Bendat & Piersol -- Random Data: Analysis and Measurement
            Procedures, John Wiley & Sons (1986)

        kwargs control the :class:`~matplotlib.lines.Line2D`
        properties of the coherence plot:

        %(Line2D)s

        **Example:**

        .. plot:: mpl_examples/pylab_examples/cohere_demo.py
        """
        if not self._hold:
            self.cla()
        cxy, freqs = mlab.cohere(x=x, y=y, NFFT=NFFT, Fs=Fs, detrend=detrend,
                                 window=window, noverlap=noverlap,
                                 scale_by_freq=scale_by_freq)
        freqs += Fc

        self.plot(freqs, cxy, **kwargs)
        self.set_xlabel('Frequency')
        self.set_ylabel('Coherence')
        self.grid(True)

        return cxy, freqs

    @docstring.dedent_interpd
    def specgram(self, x, NFFT=None, Fs=None, Fc=None, detrend=None,
                 window=None, noverlap=None,
                 cmap=None, xextent=None, pad_to=None, sides=None,
                 scale_by_freq=None, mode=None, scale=None,
                 vmin=None, vmax=None, **kwargs):
        """
        Plot a spectrogram.

        Call signature::

          specgram(x, NFFT=256, Fs=2, Fc=0, detrend=mlab.detrend_none,
                   window=mlab.window_hanning, noverlap=128,
                   cmap=None, xextent=None, pad_to=None, sides='default',
                   scale_by_freq=None, mode='default', scale='default',
                   **kwargs)

        Compute and plot a spectrogram of data in *x*.  Data are split into
        *NFFT* length segments and the spectrum of each section is
        computed.  The windowing function *window* is applied to each
        segment, and the amount of overlap of each segment is
        specified with *noverlap*. The spectrogram is plotted as a colormap
        (using imshow).

        *x*: 1-D array or sequence
            Array or sequence containing the data

        %(Spectral)s

        %(PSD)s

          *mode*: [ 'default' | 'psd' | 'magnitude' | 'angle' | 'phase' ]
            What sort of spectrum to use.  Default is 'psd'. which takes
            the power spectral density.  'complex' returns the complex-valued
            frequency spectrum.  'magnitude' returns the magnitude spectrum.
            'angle' returns the phase spectrum without unwrapping.  'phase'
            returns the phase spectrum with unwrapping.

          *noverlap*: integer
            The number of points of overlap between blocks.  The
            default value is 128.

          *scale*: [ 'default' | 'linear' | 'dB' ]
            The scaling of the values in the *spec*.  'linear' is no scaling.
            'dB' returns the values in dB scale.  When *mode* is 'psd',
            this is dB power (10 * log10).  Otherwise this is dB amplitude
            (20 * log10). 'default' is 'dB' if *mode* is 'psd' or
            'magnitude' and 'linear' otherwise.  This must be 'linear'
            if *mode* is 'angle' or 'phase'.

          *Fc*: integer
            The center frequency of *x* (defaults to 0), which offsets
            the x extents of the plot to reflect the frequency range used
            when a signal is acquired and then filtered and downsampled to
            baseband.

          *cmap*:
            A :class:`matplotlib.colors.Colormap` instance; if *None*, use
            default determined by rc

          *xextent*:
            The image extent along the x-axis. xextent = (xmin,xmax)
            The default is (0,max(bins)), where bins is the return
            value from :func:`~matplotlib.mlab.specgram`

          *kwargs*:
            Additional kwargs are passed on to imshow which makes the
            specgram image

        .. note::

            *detrend* and *scale_by_freq* only apply when *mode* is set to
            'psd'

        Returns the tuple (*spectrum*, *freqs*, *t*, *im*):

          *spectrum*: 2-D array
            columns are the periodograms of successive segments

          *freqs*: 1-D array
            The frequencies corresponding to the rows in *spectrum*

          *t*: 1-D array
            The times corresponding to midpoints of segments (i.e the columns
            in *spectrum*)

          *im*: instance of class :class:`~matplotlib.image.AxesImage`
            The image created by imshow containing the spectrogram

        **Example:**

        .. plot:: mpl_examples/pylab_examples/specgram_demo.py

        .. seealso::

            :func:`psd`
                :func:`psd` differs in the default overlap; in returning
                the mean of the segment periodograms; in not returning
                times; and in generating a line plot instead of colormap.

            :func:`magnitude_spectrum`
                A single spectrum, similar to having a single segment when
                *mode* is 'magnitude'.  Plots a line instead of a colormap.

            :func:`angle_spectrum`
                A single spectrum, similar to having a single segment when
                *mode* is 'angle'.  Plots a line instead of a colormap.

            :func:`phase_spectrum`
                A single spectrum, similar to having a single segment when
                *mode* is 'phase'.  Plots a line instead of a colormap.
        """
        if not self._hold:
            self.cla()

        if Fc is None:
            Fc = 0

        if mode == 'complex':
            raise ValueError('Cannot plot a complex specgram')

        if scale is None or scale == 'default':
            if mode in ['angle', 'phase']:
                scale = 'linear'
            else:
                scale = 'dB'
        elif mode in ['angle', 'phase'] and scale == 'dB':
            raise ValueError('Cannot use dB scale with angle or phase mode')

        spec, freqs, t = mlab.specgram(x=x, NFFT=NFFT, Fs=Fs,
                                       detrend=detrend, window=window,
                                       noverlap=noverlap, pad_to=pad_to,
                                       sides=sides,
                                       scale_by_freq=scale_by_freq,
                                       mode=mode)

        if scale == 'linear':
            Z = spec
        elif scale == 'dB':
            if mode is None or mode == 'default' or mode == 'psd':
                Z = 10. * np.log10(spec)
            else:
                Z = 20. * np.log10(spec)
        else:
            raise ValueError('Unknown scale %s', scale)

        Z = np.flipud(Z)

        if xextent is None:
            xextent = 0, np.amax(t)
        xmin, xmax = xextent
        freqs += Fc
        extent = xmin, xmax, freqs[0], freqs[-1]
        im = self.imshow(Z, cmap, extent=extent, vmin=vmin, vmax=vmax,
                         **kwargs)
        self.axis('auto')

        return spec, freqs, t, im

    def spy(self, Z, precision=0, marker=None, markersize=None,
            aspect='equal', origin="upper", **kwargs):
        """
        Plot the sparsity pattern on a 2-D array.

        ``spy(Z)`` plots the sparsity pattern of the 2-D array *Z*.

        Parameters
        ----------

        Z : sparse array (n, m)
            The array to be plotted.

        precision : float, optional, default: 0
            If *precision* is 0, any non-zero value will be plotted; else,
            values of :math:`|Z| > precision` will be plotted.

            For :class:`scipy.sparse.spmatrix` instances, there is a special
            case: if *precision* is 'present', any value present in the array
            will be plotted, even if it is identically zero.

        origin : ["upper", "lower"], optional, default: "upper"
            Place the [0,0] index of the array in the upper left or lower left
            corner of the axes.

        aspect : ['auto' | 'equal' | scalar], optional, default: "equal"

            If 'equal', and `extent` is None, changes the axes aspect ratio to
            match that of the image. If `extent` is not `None`, the axes
            aspect ratio is changed to match that of the extent.


            If 'auto', changes the image aspect ratio to match that of the
            axes.

            If None, default to rc ``image.aspect`` value.

        Two plotting styles are available: image or marker. Both
        are available for full arrays, but only the marker style
        works for :class:`scipy.sparse.spmatrix` instances.

        If *marker* and *markersize* are *None*, an image will be
        returned and any remaining kwargs are passed to
        :func:`~matplotlib.pyplot.imshow`; else, a
        :class:`~matplotlib.lines.Line2D` object will be returned with
        the value of marker determining the marker type, and any
        remaining kwargs passed to the
        :meth:`~matplotlib.axes.Axes.plot` method.

        If *marker* and *markersize* are *None*, useful kwargs include:

        * *cmap*
        * *alpha*

        See also
        --------
        imshow : for image options.
        plot : for plotting options
        """
        if marker is None and markersize is None and hasattr(Z, 'tocoo'):
            marker = 's'
        if marker is None and markersize is None:
            Z = np.asarray(Z)
            mask = np.absolute(Z) > precision

            if 'cmap' not in kwargs:
                kwargs['cmap'] = mcolors.ListedColormap(['w', 'k'],
                                                        name='binary')
            nr, nc = Z.shape
            extent = [-0.5, nc - 0.5, nr - 0.5, -0.5]
            ret = self.imshow(mask, interpolation='nearest', aspect=aspect,
                                extent=extent, origin=origin, **kwargs)
        else:
            if hasattr(Z, 'tocoo'):
                c = Z.tocoo()
                if precision == 'present':
                    y = c.row
                    x = c.col
                else:
                    nonzero = np.absolute(c.data) > precision
                    y = c.row[nonzero]
                    x = c.col[nonzero]
            else:
                Z = np.asarray(Z)
                nonzero = np.absolute(Z) > precision
                y, x = np.nonzero(nonzero)
            if marker is None:
                marker = 's'
            if markersize is None:
                markersize = 10
            marks = mlines.Line2D(x, y, linestyle='None',
                         marker=marker, markersize=markersize, **kwargs)
            self.add_line(marks)
            nr, nc = Z.shape
            self.set_xlim(xmin=-0.5, xmax=nc - 0.5)
            self.set_ylim(ymin=nr - 0.5, ymax=-0.5)
            self.set_aspect(aspect)
            ret = marks
        self.title.set_y(1.05)
        self.xaxis.tick_top()
        self.xaxis.set_ticks_position('both')
        self.xaxis.set_major_locator(mticker.MaxNLocator(nbins=9,
                                                 steps=[1, 2, 5, 10],
                                                 integer=True))
        self.yaxis.set_major_locator(mticker.MaxNLocator(nbins=9,
                                                 steps=[1, 2, 5, 10],
                                                 integer=True))
        return ret

    def matshow(self, Z, **kwargs):
        """
        Plot a matrix or array as an image.

        The matrix will be shown the way it would be printed, with the first
        row at the top.  Row and column numbering is zero-based.

        Parameters
        ----------
        Z : array_like shape (n, m)
            The matrix to be displayed.

        Returns
        -------
        image : `~matplotlib.image.AxesImage`

        Other parameters
        ----------------
        kwargs : `~matplotlib.axes.Axes.imshow` arguments
            Sets `origin` to 'upper', 'interpolation' to 'nearest' and
            'aspect' to equal.

        See also
        --------
        imshow : plot an image

        Examples
        --------
        .. plot:: mpl_examples/pylab_examples/matshow.py

        """
        Z = np.asanyarray(Z)
        nr, nc = Z.shape
        kw = {'origin': 'upper',
              'interpolation': 'nearest',
              'aspect': 'equal'}          # (already the imshow default)
        kw.update(kwargs)
        im = self.imshow(Z, **kw)
        self.title.set_y(1.05)
        self.xaxis.tick_top()
        self.xaxis.set_ticks_position('both')
        self.xaxis.set_major_locator(mticker.MaxNLocator(nbins=9,
                                                 steps=[1, 2, 5, 10],
                                                 integer=True))
        self.yaxis.set_major_locator(mticker.MaxNLocator(nbins=9,
                                                 steps=[1, 2, 5, 10],
                                                 integer=True))
        return im

    def violinplot(self, dataset, positions=None, vert=True, widths=0.5,
                   showmeans=False, showextrema=True, showmedians=False,
                   points=100, bw_method=None):
        """Make a violin plot.

        Call signature::

          violinplot(dataset, positions=None, vert=True, widths=0.5,
                     showmeans=False, showextrema=True, showmedians=False,
                     points=100, bw_method=None):

        Make a violin plot for each column of *dataset* or each vector in
        sequence *dataset*.  Each filled area extends to represent the
        entire data range, with optional lines at the mean, the median,
        the minimum, and the maximum.

        Parameters
        ----------
        dataset : Array or a sequence of vectors.
          The input data.

        positions : array-like, default = [1, 2, ..., n]
          Sets the positions of the violins. The ticks and limits are
          automatically set to match the positions.

        vert : bool, default = True.
          If true, creates a vertical violin plot.
          Otherwise, creates a horizontal violin plot.

        widths : array-like, default = 0.5
          Either a scalar or a vector that sets the maximal width of
          each violin. The default is 0.5, which uses about half of the
          available horizontal space.

        showmeans : bool, default = False
          If `True`, will toggle rendering of the means.

        showextrema : bool, default = True
          If `True`, will toggle rendering of the extrema.

        showmedians : bool, default = False
          If `True`, will toggle rendering of the medians.

        points : scalar, default = 100
          Defines the number of points to evaluate each of the
          gaussian kernel density estimations at.

        bw_method : str, scalar or callable, optional
          The method used to calculate the estimator bandwidth.  This can be
          'scott', 'silverman', a scalar constant or a callable.  If a
          scalar, this will be used directly as `kde.factor`.  If a
          callable, it should take a `GaussianKDE` instance as its only
          parameter and return a scalar. If None (default), 'scott' is used.

        Returns
        -------

        result : dict
          A dictionary mapping each component of the violinplot to a
          list of the corresponding collection instances created. The
          dictionary has the following keys:

            - ``bodies``: A list of the
              :class:`matplotlib.collections.PolyCollection` instances
              containing the filled area of each violin.

            - ``means``: A
              :class:`matplotlib.collections.LineCollection` instance
              created to identify the mean values of each of the
              violin's distribution.

            - ``mins``: A
              :class:`matplotlib.collections.LineCollection` instance
              created to identify the bottom of each violin's
              distribution.

            - ``maxes``: A
              :class:`matplotlib.collections.LineCollection` instance
              created to identify the top of each violin's
              distribution.

            - ``bars``: A
              :class:`matplotlib.collections.LineCollection` instance
              created to identify the centers of each violin's
              distribution.

            - ``medians``: A
              :class:`matplotlib.collections.LineCollection` instance
              created to identify the median values of each of the
              violin's distribution.
        """

        def _kde_method(X, coords):
            kde = mlab.GaussianKDE(X, bw_method)
            return kde.evaluate(coords)

        vpstats = cbook.violin_stats(dataset, _kde_method, points=points)
        return self.violin(vpstats, positions=positions, vert=vert,
                           widths=widths, showmeans=showmeans,
                           showextrema=showextrema, showmedians=showmedians)

    def violin(self, vpstats, positions=None, vert=True, widths=0.5,
               showmeans=False, showextrema=True, showmedians=False):
        """Drawing function for violin plots.

        Call signature::

          violin(vpstats, positions=None, vert=True, widths=0.5,
                 showmeans=False, showextrema=True, showmedians=False):

        Draw a violin plot for each column of `vpstats`. Each filled area
        extends to represent the entire data range, with optional lines at the
        mean, the median, the minimum, and the maximum.

        Parameters
        ----------

        vpstats : list of dicts
          A list of dictionaries containing stats for each violin plot.
          Required keys are:

          - ``coords``: A list of scalars containing the coordinates that
            the violin's kernel density estimate were evaluated at.

          - ``vals``: A list of scalars containing the values of the
            kernel density estimate at each of the coordinates given
            in *coords*.

          - ``mean``: The mean value for this violin's dataset.

          - ``median``: The median value for this violin's dataset.

          - ``min``: The minimum value for this violin's dataset.

          - ``max``: The maximum value for this violin's dataset.

        positions : array-like, default = [1, 2, ..., n]
          Sets the positions of the violins. The ticks and limits are
          automatically set to match the positions.

        vert : bool, default = True.
          If true, plots the violins veritcally.
          Otherwise, plots the violins horizontally.

        widths : array-like, default = 0.5
          Either a scalar or a vector that sets the maximal width of
          each violin. The default is 0.5, which uses about half of the
          available horizontal space.

        showmeans : bool, default = False
          If true, will toggle rendering of the means.

        showextrema : bool, default = True
          If true, will toggle rendering of the extrema.

        showmedians : bool, default = False
          If true, will toggle rendering of the medians.

        Returns
        -------
        result : dict
          A dictionary mapping each component of the violinplot to a
          list of the corresponding collection instances created. The
          dictionary has the following keys:

            - ``bodies``: A list of the
              :class:`matplotlib.collections.PolyCollection` instances
              containing the filled area of each violin.

            - ``means``: A
              :class:`matplotlib.collections.LineCollection` instance
              created to identify the mean values of each of the
              violin's distribution.

            - ``mins``: A
              :class:`matplotlib.collections.LineCollection` instance
              created to identify the bottom of each violin's
              distribution.

            - ``maxes``: A
              :class:`matplotlib.collections.LineCollection` instance
              created to identify the top of each violin's
              distribution.

            - ``bars``: A
              :class:`matplotlib.collections.LineCollection` instance
              created to identify the centers of each violin's
              distribution.

            - ``medians``: A
              :class:`matplotlib.collections.LineCollection` instance
              created to identify the median values of each of the
              violin's distribution.

        """

        # Statistical quantities to be plotted on the violins
        means = []
        mins = []
        maxes = []
        medians = []

        # Collections to be returned
        artists = {}

        N = len(vpstats)
        datashape_message = ("List of violinplot statistics and `{0}` "
                             "values must have the same length")

        # Validate positions
        if positions is None:
            positions = range(1, N + 1)
        elif len(positions) != N:
            raise ValueError(datashape_message.format("positions"))

        # Validate widths
        if np.isscalar(widths):
            widths = [widths] * N
        elif len(widths) != N:
            raise ValueError(datashape_message.format("widths"))

        # Calculate ranges for statistics lines
        pmins = -0.25 * np.array(widths) + positions
        pmaxes = 0.25 * np.array(widths) + positions

        # Check whether we are rendering vertically or horizontally
        if vert:
            fill = self.fill_betweenx
            perp_lines = self.hlines
            par_lines = self.vlines
        else:
            fill = self.fill_between
            perp_lines = self.vlines
            par_lines = self.hlines

        # Render violins
        bodies = []
        for stats, pos, width in zip(vpstats, positions, widths):
            # The 0.5 factor reflects the fact that we plot from v-p to
            # v+p
            vals = np.array(stats['vals'])
            vals = 0.5 * width * vals / vals.max()
            bodies += [fill(stats['coords'],
                            -vals + pos,
                            vals + pos,
                            facecolor='y',
                            alpha=0.3)]
            means.append(stats['mean'])
            mins.append(stats['min'])
            maxes.append(stats['max'])
            medians.append(stats['median'])
        artists['bodies'] = bodies

        # Render means
        if showmeans:
            artists['cmeans'] = perp_lines(means, pmins, pmaxes, colors='r')

        # Render extrema
        if showextrema:
            artists['cmaxes'] = perp_lines(maxes, pmins, pmaxes, colors='r')
            artists['cmins'] = perp_lines(mins, pmins, pmaxes, colors='r')
            artists['cbars'] = par_lines(positions, mins, maxes, colors='r')

        # Render medians
        if showmedians:
            artists['cmedians'] = perp_lines(medians,
                                             pmins,
                                             pmaxes,
                                             colors='r')

        return artists

    def tricontour(self, *args, **kwargs):
        return mtri.tricontour(self, *args, **kwargs)
    tricontour.__doc__ = mtri.TriContourSet.tricontour_doc

    def tricontourf(self, *args, **kwargs):
        return mtri.tricontourf(self, *args, **kwargs)
    tricontourf.__doc__ = mtri.TriContourSet.tricontour_doc

    def tripcolor(self, *args, **kwargs):
        return mtri.tripcolor(self, *args, **kwargs)
    tripcolor.__doc__ = mtri.tripcolor.__doc__

    def triplot(self, *args, **kwargs):
        return mtri.triplot(self, *args, **kwargs)
    triplot.__doc__ = mtri.triplot.__doc__