tile.py

"""
Quantilization functions and related stuff
"""

from pandas.types.missing import isnull
from pandas.types.common import (is_float, is_integer,
                                 is_scalar)

from pandas.core.api import Series
from pandas.core.categorical import Categorical
import pandas.core.algorithms as algos
import pandas.core.nanops as nanops
from pandas.compat import zip

import numpy as np


def cut(x, bins, right=True, labels=None, retbins=False, precision=3,
        include_lowest=False):
    """
    Return indices of half-open bins to which each value of `x` belongs.

    Parameters
    ----------
    x : array-like
        Input array to be binned. It has to be 1-dimensional.
    bins : int or sequence of scalars
        If `bins` is an int, it defines the number of equal-width bins in the
        range of `x`. However, in this case, the range of `x` is extended
        by .1% on each side to include the min or max values of `x`. If
        `bins` is a sequence it defines the bin edges allowing for
        non-uniform bin width. No extension of the range of `x` is done in
        this case.
    right : bool, optional
        Indicates whether the bins include the rightmost edge or not. If
        right == True (the default), then the bins [1,2,3,4] indicate
        (1,2], (2,3], (3,4].
    labels : array or boolean, default None
        Used as labels for the resulting bins. Must be of the same length as
        the resulting bins. If False, return only integer indicators of the
        bins.
    retbins : bool, optional
        Whether to return the bins or not. Can be useful if bins is given
        as a scalar.
    precision : int
        The precision at which to store and display the bins labels
    include_lowest : bool
        Whether the first interval should be left-inclusive or not.

    Returns
    -------
    out : Categorical or Series or array of integers if labels is False
        The return type (Categorical or Series) depends on the input: a Series
        of type category if input is a Series else Categorical. Bins are
        represented as categories when categorical data is returned.
    bins : ndarray of floats
        Returned only if `retbins` is True.

    Notes
    -----
    The `cut` function can be useful for going from a continuous variable to
    a categorical variable. For example, `cut` could convert ages to groups
    of age ranges.

    Any NA values will be NA in the result.  Out of bounds values will be NA in
    the resulting Categorical object


    Examples
    --------
    >>> pd.cut(np.array([.2, 1.4, 2.5, 6.2, 9.7, 2.1]), 3, retbins=True)
    ([(0.191, 3.367], (0.191, 3.367], (0.191, 3.367], (3.367, 6.533],
      (6.533, 9.7], (0.191, 3.367]]
    Categories (3, object): [(0.191, 3.367] < (3.367, 6.533] < (6.533, 9.7]],
    array([ 0.1905    ,  3.36666667,  6.53333333,  9.7       ]))
    >>> pd.cut(np.array([.2, 1.4, 2.5, 6.2, 9.7, 2.1]), 3,
               labels=["good","medium","bad"])
    [good, good, good, medium, bad, good]
    Categories (3, object): [good < medium < bad]
    >>> pd.cut(np.ones(5), 4, labels=False)
    array([1, 1, 1, 1, 1], dtype=int64)
    """
    # NOTE: this binning code is changed a bit from histogram for var(x) == 0
    if not np.iterable(bins):
        if is_scalar(bins) and bins < 1:
            raise ValueError("`bins` should be a positive integer.")
        try:  # for array-like
            sz = x.size
        except AttributeError:
            x = np.asarray(x)
            sz = x.size
        if sz == 0:
            raise ValueError('Cannot cut empty array')
            # handle empty arrays. Can't determine range, so use 0-1.
            # rng = (0, 1)
        else:
            rng = (nanops.nanmin(x), nanops.nanmax(x))
        mn, mx = [mi + 0.0 for mi in rng]

        if mn == mx:  # adjust end points before binning
            mn -= .001 * mn
            mx += .001 * mx
            bins = np.linspace(mn, mx, bins + 1, endpoint=True)
        else:  # adjust end points after binning
            bins = np.linspace(mn, mx, bins + 1, endpoint=True)
            adj = (mx - mn) * 0.001  # 0.1% of the range
            if right:
                bins[0] -= adj
            else:
                bins[-1] += adj

    else:
        bins = np.asarray(bins)
        if (np.diff(bins) < 0).any():
            raise ValueError('bins must increase monotonically.')

    return _bins_to_cuts(x, bins, right=right, labels=labels,
                         retbins=retbins, precision=precision,
                         include_lowest=include_lowest)


def qcut(x, q, labels=None, retbins=False, precision=3):
    """
    Quantile-based discretization function. Discretize variable into
    equal-sized buckets based on rank or based on sample quantiles. For example
    1000 values for 10 quantiles would produce a Categorical object indicating
    quantile membership for each data point.

    Parameters
    ----------
    x : ndarray or Series
    q : integer or array of quantiles
        Number of quantiles. 10 for deciles, 4 for quartiles, etc. Alternately
        array of quantiles, e.g. [0, .25, .5, .75, 1.] for quartiles
    labels : array or boolean, default None
        Used as labels for the resulting bins. Must be of the same length as
        the resulting bins. If False, return only integer indicators of the
        bins.
    retbins : bool, optional
        Whether to return the bins or not. Can be useful if bins is given
        as a scalar.
    precision : int
        The precision at which to store and display the bins labels

    Returns
    -------
    out : Categorical or Series or array of integers if labels is False
        The return type (Categorical or Series) depends on the input: a Series
        of type category if input is a Series else Categorical. Bins are
        represented as categories when categorical data is returned.
    bins : ndarray of floats
        Returned only if `retbins` is True.

    Notes
    -----
    Out of bounds values will be NA in the resulting Categorical object

    Examples
    --------
    >>> pd.qcut(range(5), 4)
    [[0, 1], [0, 1], (1, 2], (2, 3], (3, 4]]
    Categories (4, object): [[0, 1] < (1, 2] < (2, 3] < (3, 4]]
    >>> pd.qcut(range(5), 3, labels=["good","medium","bad"])
    [good, good, medium, bad, bad]
    Categories (3, object): [good < medium < bad]
    >>> pd.qcut(range(5), 4, labels=False)
    array([0, 0, 1, 2, 3], dtype=int64)
    """
    if is_integer(q):
        quantiles = np.linspace(0, 1, q + 1)
    else:
        quantiles = q
    bins = algos.quantile(x, quantiles)
    return _bins_to_cuts(x, bins, labels=labels, retbins=retbins,
                         precision=precision, include_lowest=True)


def _bins_to_cuts(x, bins, right=True, labels=None, retbins=False,
                  precision=3, name=None, include_lowest=False):
    x_is_series = isinstance(x, Series)
    series_index = None

    if x_is_series:
        series_index = x.index
        if name is None:
            name = x.name

    x = np.asarray(x)

    side = 'left' if right else 'right'
    ids = bins.searchsorted(x, side=side)

    if len(algos.unique(bins)) < len(bins):
        raise ValueError('Bin edges must be unique: %s' % repr(bins))

    if include_lowest:
        ids[x == bins[0]] = 1

    na_mask = isnull(x) | (ids == len(bins)) | (ids == 0)
    has_nas = na_mask.any()

    if labels is not False:
        if labels is None:
            increases = 0
            while True:
                try:
                    levels = _format_levels(bins, precision, right=right,
                                            include_lowest=include_lowest)
                except ValueError:
                    increases += 1
                    precision += 1
                    if increases >= 20:
                        raise
                else:
                    break

        else:
            if len(labels) != len(bins) - 1:
                raise ValueError('Bin labels must be one fewer than '
                                 'the number of bin edges')
            levels = labels

        levels = np.asarray(levels, dtype=object)
        np.putmask(ids, na_mask, 0)
        fac = Categorical(ids - 1, levels, ordered=True, fastpath=True)
    else:
        fac = ids - 1
        if has_nas:
            fac = fac.astype(np.float64)
            np.putmask(fac, na_mask, np.nan)

    if x_is_series:
        fac = Series(fac, index=series_index, name=name)

    if not retbins:
        return fac

    return fac, bins


def _format_levels(bins, prec, right=True,
                   include_lowest=False):
    fmt = lambda v: _format_label(v, precision=prec)
    if right:
        levels = []
        for a, b in zip(bins, bins[1:]):
            fa, fb = fmt(a), fmt(b)

            if a != b and fa == fb:
                raise ValueError('precision too low')

            formatted = '(%s, %s]' % (fa, fb)

            levels.append(formatted)

        if include_lowest:
            levels[0] = '[' + levels[0][1:]
    else:
        levels = ['[%s, %s)' % (fmt(a), fmt(b))
                  for a, b in zip(bins, bins[1:])]

    return levels


def _format_label(x, precision=3):
    fmt_str = '%%.%dg' % precision
    if np.isinf(x):
        return str(x)
    elif is_float(x):
        frac, whole = np.modf(x)
        sgn = '-' if x < 0 else ''
        whole = abs(whole)
        if frac != 0.0:
            val = fmt_str % frac

            # rounded up or down
            if '.' not in val:
                if x < 0:
                    return '%d' % (-whole - 1)
                else:
                    return '%d' % (whole + 1)

            if 'e' in val:
                return _trim_zeros(fmt_str % x)
            else:
                val = _trim_zeros(val)
                if '.' in val:
                    return sgn + '.'.join(('%d' % whole, val.split('.')[1]))
                else:  # pragma: no cover
                    return sgn + '.'.join(('%d' % whole, val))
        else:
            return sgn + '%0.f' % whole
    else:
        return str(x)


def _trim_zeros(x):
    while len(x) > 1 and x[-1] == '0':
        x = x[:-1]
    if len(x) > 1 and x[-1] == '.':
        x = x[:-1]
    return x