topomap.py

"""Functions to plot M/EEG data e.g. topographies."""

# Authors: Alexandre Gramfort <alexandre.gramfort@inria.fr>
#          Denis Engemann <denis.engemann@gmail.com>
#          Martin Luessi <mluessi@nmr.mgh.harvard.edu>
#          Eric Larson <larson.eric.d@gmail.com>
#          Robert Luke <mail@robertluke.net>
#
# License: Simplified BSD

import copy
import itertools
from functools import partial
from numbers import Integral
import warnings

import numpy as np

from ..baseline import rescale
from ..channels.channels import _get_ch_type
from ..channels.layout import (
    _find_topomap_coords, find_layout, _pair_grad_sensors, _merge_ch_data)
from ..defaults import _EXTRAPOLATE_DEFAULT, _BORDER_DEFAULT
from ..io.pick import (pick_types, _picks_by_type, pick_info, pick_channels,
                       _pick_data_channels, _picks_to_idx, _get_channel_types,
                       _MEG_CH_TYPES_SPLIT)
from ..utils import (_clean_names, _time_mask, verbose, logger, warn, fill_doc,
                     _validate_type, _check_sphere, _check_option, _is_numeric)
from .utils import (tight_layout, _setup_vmin_vmax, _prepare_trellis,
                    _check_delayed_ssp, _draw_proj_checkbox, figure_nobar,
                    plt_show, _process_times, DraggableColorbar,
                    _validate_if_list_of_axes, _setup_cmap, _check_time_unit)
from ..time_frequency import psd_multitaper
from ..defaults import _handle_default
from ..transforms import apply_trans, invert_transform
from ..io.meas_info import Info, _simplify_info
from ..io.proj import Projection


_fnirs_types = ('hbo', 'hbr', 'fnirs_cw_amplitude', 'fnirs_od')


def _adjust_meg_sphere(sphere, info, ch_type):
    sphere = _check_sphere(sphere, info)
    assert ch_type is not None
    if ch_type in ('mag', 'grad', 'planar1', 'planar2'):
        # move sphere X/Y (head coords) to device X/Y space
        if info['dev_head_t'] is not None:
            head_dev_t = invert_transform(info['dev_head_t'])
            sphere[:3] = apply_trans(head_dev_t, sphere[:3])
            # Set the sphere Z=0 because all this really affects is flattening.
            # We could make the head size change as a function of depth in
            # the helmet like:
            #
            #     sphere[2] /= -5
            #
            # but let's just assume some orthographic rather than parallel
            # projection for explicitness / simplicity.
            sphere[2] = 0.
        clip_origin = (0., 0.)
    else:
        clip_origin = sphere[:2].copy()
    return sphere, clip_origin


def _prepare_topomap_plot(inst, ch_type, sphere=None):
    """Prepare topo plot."""
    info = copy.deepcopy(inst if isinstance(inst, Info) else inst.info)
    sphere, clip_origin = _adjust_meg_sphere(sphere, info, ch_type)

    clean_ch_names = _clean_names(info['ch_names'])
    for ii, this_ch in enumerate(info['chs']):
        this_ch['ch_name'] = clean_ch_names[ii]
    info['bads'] = _clean_names(info['bads'])
    for comp in info['comps']:
        comp['data']['col_names'] = _clean_names(comp['data']['col_names'])

    info._update_redundant()
    info._check_consistency()

    # special case for merging grad channels
    layout = find_layout(info)
    if (ch_type == 'grad' and layout is not None and
            (layout.kind.startswith('Vectorview') or
             layout.kind.startswith('Neuromag_122'))):
        picks, _ = _pair_grad_sensors(info, layout)
        pos = _find_topomap_coords(info, picks[::2], sphere=sphere)
        merge_channels = True
    elif ch_type in _fnirs_types:
        # fNIRS data commonly has overlapping channels, so deal with separately
        picks, pos, merge_channels, overlapping_channels = \
            _average_fnirs_overlaps(info, ch_type, sphere)
    else:
        merge_channels = False
        if ch_type == 'eeg':
            picks = pick_types(info, meg=False, eeg=True, ref_meg=False,
                               exclude='bads')
        elif ch_type == 'csd':
            picks = pick_types(info, meg=False, csd=True, ref_meg=False,
                               exclude='bads')
        else:
            picks = pick_types(info, meg=ch_type, ref_meg=False,
                               exclude='bads')

        if len(picks) == 0:
            raise ValueError("No channels of type %r" % ch_type)

        pos = _find_topomap_coords(info, picks, sphere=sphere)

    ch_names = [info['ch_names'][k] for k in picks]
    if ch_type in _fnirs_types:
        # Remove the chroma label type for cleaner labeling.
        ch_names = [k[:-4] for k in ch_names]

    if merge_channels:
        if ch_type == 'grad':
            # change names so that vectorview combined grads appear as MEG014x
            # instead of MEG0142 or MEG0143 which are the 2 planar grads.
            ch_names = [ch_names[k][:-1] + 'x' for k in
                        range(0, len(ch_names), 2)]
        else:
            assert ch_type in _fnirs_types
            # Modify the nirs channel names to indicate they are to be merged
            # New names will have the form  S1_D1xS2_D2
            # More than two channels can overlap and be merged
            for set in overlapping_channels:
                idx = ch_names.index(set[0][:-4])
                new_name = 'x'.join(s[:-4] for s in set)
                ch_names[idx] = new_name

    pos = np.array(pos)[:, :2]  # 2D plot, otherwise interpolation bugs
    return picks, pos, merge_channels, ch_names, ch_type, sphere, clip_origin


def _average_fnirs_overlaps(info, ch_type, sphere):

    from scipy.spatial.distance import pdist, squareform

    picks = pick_types(info, meg=False, ref_meg=False,
                       fnirs=ch_type, exclude='bads')
    chs = [info['chs'][i] for i in picks]
    locs3d = np.array([ch['loc'][:3] for ch in chs])
    dist = pdist(locs3d)

    # Store the sets of channels to be merged
    overlapping_channels = list()
    # Channels to be excluded from picks, as will be removed after merging
    channels_to_exclude = list()

    if len(locs3d) > 1 and np.min(dist) < 1e-10:

        overlapping_mask = np.triu(squareform(dist < 1e-10))
        for chan_idx in range(overlapping_mask.shape[0]):
            already_overlapped = list(itertools.chain.from_iterable(
                overlapping_channels))
            if overlapping_mask[chan_idx].any() and \
                    (chs[chan_idx]['ch_name'] not in already_overlapped):
                # Determine the set of channels to be combined. Ensure the
                # first listed channel is the one to be replaced with merge
                overlapping_set = [chs[i]['ch_name'] for i in
                                   np.where(overlapping_mask[chan_idx])[0]]
                overlapping_set = np.insert(overlapping_set, 0,
                                            (chs[chan_idx]['ch_name']))
                overlapping_channels.append(overlapping_set)
                channels_to_exclude.append(overlapping_set[1:])

        exclude = list(itertools.chain.from_iterable(channels_to_exclude))
        [exclude.append(bad) for bad in info['bads']]
        picks = pick_types(info, meg=False, ref_meg=False, fnirs=ch_type,
                           exclude=exclude)
        pos = _find_topomap_coords(info, picks, sphere=sphere)
        picks = pick_types(info, meg=False, ref_meg=False, fnirs=ch_type)
        # Overload the merge_channels variable as this is returned to calling
        # function and indicates that merging of data is required
        merge_channels = overlapping_channels

    else:
        picks = pick_types(info, meg=False, ref_meg=False, fnirs=ch_type,
                           exclude='bads')
        merge_channels = False
        pos = _find_topomap_coords(info, picks, sphere=sphere)

    return picks, pos, merge_channels, overlapping_channels


def _plot_update_evoked_topomap(params, bools):
    """Update topomaps."""
    projs = [proj for ii, proj in enumerate(params['projs'])
             if ii in np.where(bools)[0]]

    params['proj_bools'] = bools
    new_evoked = params['evoked'].copy()
    new_evoked.info['projs'] = []
    new_evoked.add_proj(projs)
    new_evoked.apply_proj()

    data = new_evoked.data[:, params['time_idx']] * params['scale']
    if params['merge_channels']:
        data, _ = _merge_ch_data(data, 'grad', [])

    interp = params['interp']
    new_contours = list()
    for cont, ax, im, d in zip(params['contours_'], params['axes'],
                               params['images'], data.T):
        Zi = interp.set_values(d)()
        im.set_data(Zi)
        # must be removed and re-added
        if len(cont.collections) > 0:
            tp = cont.collections[0]
            visible = tp.get_visible()
            patch_ = tp.get_clip_path()
            color = tp.get_color()
            lw = tp.get_linewidth()
        for tp in cont.collections:
            tp.remove()
        cont = ax.contour(interp.Xi, interp.Yi, Zi, params['contours'],
                          colors=color, linewidths=lw)
        for tp in cont.collections:
            tp.set_visible(visible)
            tp.set_clip_path(patch_)
        new_contours.append(cont)
    params['contours_'] = new_contours

    params['fig'].canvas.draw()


def _add_colorbar(ax, im, cmap, side="right", pad=.05, title=None,
                  format=None, size="5%"):
    """Add a colorbar to an axis."""
    import matplotlib.pyplot as plt
    from mpl_toolkits.axes_grid1 import make_axes_locatable
    divider = make_axes_locatable(ax)
    cax = divider.append_axes(side, size=size, pad=pad)
    cbar = plt.colorbar(im, cax=cax, format=format)
    if cmap is not None and cmap[1]:
        ax.CB = DraggableColorbar(cbar, im)
    if title is not None:
        cax.set_title(title, y=1.05, fontsize=10)
    return cbar, cax


def _eliminate_zeros(proj):
    """Remove grad or mag data if only contains 0s (gh 5641)."""
    GRAD_ENDING = ('2', '3')
    MAG_ENDING = '1'

    proj = copy.deepcopy(proj)
    proj['data']['data'] = np.atleast_2d(proj['data']['data'])

    for ending in (GRAD_ENDING, MAG_ENDING):
        names = proj['data']['col_names']
        idx = [i for i, name in enumerate(names) if name.endswith(ending)]

        # if all 0, remove the 0s an their labels
        if not proj['data']['data'][0][idx].any():
            new_col_names = np.delete(np.array(names), idx).tolist()
            new_data = np.delete(np.array(proj['data']['data'][0]), idx)
            proj['data']['col_names'] = new_col_names
            proj['data']['data'] = np.array([new_data])

    proj['data']['ncol'] = len(proj['data']['col_names'])
    return proj


@fill_doc
def plot_projs_topomap(projs, info, cmap=None, sensors=True,
                       colorbar=False, res=64, size=1, show=True,
                       outlines='head', contours=6, image_interp='bilinear',
                       axes=None, vlim=(None, None),
                       sphere=None, extrapolate=_EXTRAPOLATE_DEFAULT,
                       border=_BORDER_DEFAULT):
    """Plot topographic maps of SSP projections.

    Parameters
    ----------
    projs : list of Projection
        The projections.
    info : instance of Info
        The info associated with the channels in the projectors.

        .. versionchanged:: 0.20
            The positional argument ``layout`` was deprecated and replaced
            by ``info``.
    %(proj_topomap_kwargs)s
    %(topomap_sphere_auto)s
    %(topomap_extrapolate)s

        .. versionadded:: 0.20
    %(topomap_border)s

    Returns
    -------
    fig : instance of matplotlib.figure.Figure
        Figure with a topomap subplot for each projector.

    Notes
    -----
    .. versionadded:: 0.9.0
    """
    import matplotlib.pyplot as plt
    sphere = _check_sphere(sphere, info)

    # be forgiving if `projs` isn't a list
    if isinstance(projs, Projection):
        projs = [projs]

    _validate_type(info, 'info', 'info')

    types, datas, poss, spheres, outliness, ch_typess = [], [], [], [], [], []
    for proj in projs:
        # get ch_names, ch_types, data
        proj = _eliminate_zeros(proj)  # gh 5641
        ch_names = _clean_names(proj['data']['col_names'],
                                remove_whitespace=True)
        if vlim == 'joint':
            ch_idxs = np.where(np.in1d(info['ch_names'],
                                       proj['data']['col_names']))[0]
            these_ch_types = _get_channel_types(info, ch_idxs, unique=True)
            # each projector should have only one channel type
            assert len(these_ch_types) == 1
            types.append(list(these_ch_types)[0])
        data = proj['data']['data'].ravel()
        info_names = _clean_names(info['ch_names'], remove_whitespace=True)
        picks = pick_channels(info_names, ch_names)
        if len(picks) == 0:
            raise ValueError(
                f'No channel names in info match projector {proj}')
        use_info = pick_info(info, picks)
        data_picks, pos, merge_channels, names, ch_type, this_sphere, \
            clip_origin = _prepare_topomap_plot(
                use_info, _get_ch_type(use_info, None), sphere=sphere)
        these_outlines = _make_head_outlines(
            sphere, pos, outlines, clip_origin)
        data = data[data_picks]
        if merge_channels:
            data, _ = _merge_ch_data(data, 'grad', [])
            data = data.ravel()

        # populate containers
        datas.append(data)
        poss.append(pos)
        spheres.append(this_sphere)
        outliness.append(these_outlines)
        ch_typess.append(ch_type)
        del data, pos, this_sphere, these_outlines, ch_type
    del sphere

    # setup axes
    n_projs = len(projs)
    if axes is None:
        fig, axes, ncols, nrows = _prepare_trellis(
            n_projs, ncols='auto', nrows='auto')
    elif isinstance(axes, plt.Axes):
        axes = [axes]
    if len(axes) != n_projs:
        raise RuntimeError('There must be an axes for each picked projector.')

    # handle vmin/vmax
    vlims = [None for _ in range(len(datas))]
    if vlim == 'joint':
        for _ch_type in set(types):
            idx = np.where(np.in1d(types, _ch_type))[0]
            these_data = np.concatenate(np.array(datas, dtype=object)[idx])
            norm = all(these_data >= 0)
            _vl = _setup_vmin_vmax(these_data, vmin=None, vmax=None, norm=norm)
            for _idx in idx:
                vlims[_idx] = _vl
        # make sure we got a vlim for all projs
        assert all([vl is not None for vl in vlims])
    else:
        vlims = [vlim for _ in range(len(datas))]

    # plot
    for proj, ax, _data, _pos, _vlim, _sphere, _outlines, _ch_type in zip(
            projs, axes, datas, poss, vlims, spheres, outliness, ch_typess):
        # title
        title = proj['desc']
        title = '\n'.join(title[ii:ii + 22] for ii in range(0, len(title), 22))
        ax.set_title(title, fontsize=10)
        # plot
        vmin, vmax = _vlim
        im = plot_topomap(_data, _pos[:, :2], vmin=vmin, vmax=vmax, cmap=cmap,
                          sensors=sensors, res=res, axes=ax,
                          outlines=_outlines, contours=contours,
                          image_interp=image_interp, show=False,
                          extrapolate=extrapolate, sphere=_sphere,
                          border=border, ch_type=_ch_type)[0]

        if colorbar:
            _add_colorbar(ax, im, cmap)

    fig = ax.get_figure()
    with warnings.catch_warnings(record=True):
        warnings.simplefilter('ignore')
        tight_layout(fig=fig)
    plt_show(show)
    return fig


def _make_head_outlines(sphere, pos, outlines, clip_origin):
    """Check or create outlines for topoplot."""
    assert isinstance(sphere, np.ndarray)
    x, y, _, radius = sphere
    del sphere

    if outlines in ('head', 'skirt', None):
        ll = np.linspace(0, 2 * np.pi, 101)
        head_x = np.cos(ll) * radius + x
        head_y = np.sin(ll) * radius + y
        dx = np.exp(np.arccos(np.deg2rad(12)) * 1j)
        dx, dy = dx.real, dx.imag
        nose_x = np.array([-dx, 0, dx]) * radius + x
        nose_y = np.array([dy, 1.15, dy]) * radius + y
        ear_x = np.array([.497, .510, .518, .5299, .5419, .54, .547,
                          .532, .510, .489]) * (radius * 2)
        ear_y = np.array([.0555, .0775, .0783, .0746, .0555, -.0055, -.0932,
                          -.1313, -.1384, -.1199]) * (radius * 2) + y

        if outlines is not None:
            # Define the outline of the head, ears and nose
            outlines_dict = dict(head=(head_x, head_y), nose=(nose_x, nose_y),
                                 ear_left=(ear_x + x, ear_y),
                                 ear_right=(-ear_x + x, ear_y))
        else:
            outlines_dict = dict()

        # Make the figure encompass slightly more than all points
        mask_scale = 1.25 if outlines == 'skirt' else 1.
        # We probably want to ensure it always contains our most
        # extremely positioned channels, so we do:
        mask_scale = max(
            mask_scale, np.linalg.norm(pos, axis=1).max() * 1.01 / radius)
        outlines_dict['mask_pos'] = (mask_scale * head_x, mask_scale * head_y)
        clip_radius = radius * mask_scale
        outlines_dict['clip_radius'] = (clip_radius,) * 2
        outlines_dict['clip_origin'] = clip_origin
        outlines = outlines_dict

    elif isinstance(outlines, dict):
        if 'mask_pos' not in outlines:
            raise ValueError('You must specify the coordinates of the image '
                             'mask.')
    else:
        raise ValueError('Invalid value for `outlines`.')

    return outlines


def _draw_outlines(ax, outlines):
    """Draw the outlines for a topomap."""
    outlines_ = {k: v for k, v in outlines.items()
                 if k not in ['patch']}
    for key, (x_coord, y_coord) in outlines_.items():
        if 'mask' in key or key in ('clip_radius', 'clip_origin'):
            continue
        ax.plot(x_coord, y_coord, color='k', linewidth=1, clip_on=False)
    return outlines_


def _get_extra_points(pos, extrapolate, origin, radii):
    """Get coordinates of additinal interpolation points."""
    from scipy.spatial.qhull import Delaunay
    radii = np.array(radii, float)
    assert radii.shape == (2,)
    x, y = origin
    # auto should be gone by now
    _check_option('extrapolate', extrapolate, ('head', 'box', 'local'))

    # the old method of placement - large box
    mask_pos = None
    if extrapolate == 'box':
        extremes = np.array([pos.min(axis=0), pos.max(axis=0)])
        diffs = extremes[1] - extremes[0]
        extremes[0] -= diffs
        extremes[1] += diffs
        eidx = np.array(list(itertools.product(
            *([[0] * (pos.shape[1] - 1) + [1]] * pos.shape[1]))))
        pidx = np.tile(np.arange(pos.shape[1])[np.newaxis], (len(eidx), 1))
        outer_pts = extremes[eidx, pidx]
        return outer_pts, mask_pos, Delaunay(np.concatenate((pos, outer_pts)))

    # check if positions are colinear:
    diffs = np.diff(pos, axis=0)
    with np.errstate(divide='ignore'):
        slopes = diffs[:, 1] / diffs[:, 0]
    colinear = ((slopes == slopes[0]).all() or np.isinf(slopes).all())

    # compute median inter-electrode distance
    if colinear or pos.shape[0] < 4:
        dim = 1 if diffs[:, 1].sum() > diffs[:, 0].sum() else 0
        sorting = np.argsort(pos[:, dim])
        pos_sorted = pos[sorting, :]
        diffs = np.diff(pos_sorted, axis=0)
        distances = np.linalg.norm(diffs, axis=1)
        distance = np.median(distances)
    else:
        tri = Delaunay(pos, incremental=True)
        idx1, idx2, idx3 = tri.simplices.T
        distances = np.concatenate(
            [np.linalg.norm(pos[i1, :] - pos[i2, :], axis=1)
             for i1, i2 in zip([idx1, idx2], [idx2, idx3])])
        distance = np.median(distances)

    if extrapolate == 'local':
        if colinear or pos.shape[0] < 4:
            # special case for colinear points and when there is too
            # little points for Delaunay (needs at least 3)
            edge_points = sorting[[0, -1]]
            line_len = np.diff(pos[edge_points, :], axis=0)
            unit_vec = line_len / np.linalg.norm(line_len) * distance
            unit_vec_par = unit_vec[:, ::-1] * [[-1, 1]]

            edge_pos = (pos[edge_points, :] +
                        np.concatenate([-unit_vec, unit_vec], axis=0))
            new_pos = np.concatenate([pos + unit_vec_par,
                                      pos - unit_vec_par, edge_pos], axis=0)

            if pos.shape[0] == 3:
                # there may be some new_pos points that are too close
                # to the original points
                new_pos_diff = pos[..., np.newaxis] - new_pos.T[np.newaxis, :]
                new_pos_diff = np.linalg.norm(new_pos_diff, axis=1)
                good_extra = (new_pos_diff > 0.5 * distance).all(axis=0)
                new_pos = new_pos[good_extra]

            tri = Delaunay(np.concatenate([pos, new_pos], axis=0))
            return new_pos, new_pos, tri

        # get the convex hull of data points from triangulation
        hull_pos = pos[tri.convex_hull]

        # extend the convex hull limits outwards a bit
        channels_center = pos.mean(axis=0)
        radial_dir = hull_pos - channels_center
        unit_radial_dir = radial_dir / np.linalg.norm(radial_dir, axis=-1,
                                                      keepdims=True)
        hull_extended = hull_pos + unit_radial_dir * distance
        mask_pos = hull_pos + unit_radial_dir * distance * 0.5
        hull_diff = np.diff(hull_pos, axis=1)[:, 0]
        hull_distances = np.linalg.norm(hull_diff, axis=-1)
        del channels_center

        # Construct a mask
        mask_pos = np.unique(mask_pos.reshape(-1, 2), axis=0)
        mask_center = np.mean(mask_pos, axis=0)
        mask_pos -= mask_center
        mask_pos = mask_pos[
            np.argsort(np.arctan2(mask_pos[:, 1], mask_pos[:, 0]))]
        mask_pos += mask_center

        # add points along hull edges so that the distance between points
        # is around that of average distance between channels
        add_points = list()
        eps = np.finfo('float').eps
        n_times_dist = np.round(0.25 * hull_distances / distance).astype('int')
        for n in range(2, n_times_dist.max() + 1):
            mask = n_times_dist == n
            mult = np.arange(1 / n, 1 - eps, 1 / n)[:, np.newaxis, np.newaxis]
            steps = hull_diff[mask][np.newaxis, ...] * mult
            add_points.append((hull_extended[mask, 0][np.newaxis, ...] +
                               steps).reshape((-1, 2)))

        # remove duplicates from hull_extended
        hull_extended = np.unique(hull_extended.reshape((-1, 2)), axis=0)
        new_pos = np.concatenate([hull_extended] + add_points)
    else:
        assert extrapolate == 'head'
        # return points on the head circle
        angle = np.arcsin(distance / 2 / np.mean(radii))
        points_l = np.arange(0, 2 * np.pi, angle)
        use_radii = radii * 1.1
        points_x = np.cos(points_l) * use_radii[0] + x
        points_y = np.sin(points_l) * use_radii[1] + y
        new_pos = np.stack([points_x, points_y], axis=1)
        if colinear or pos.shape[0] == 3:
            tri = Delaunay(np.concatenate([pos, new_pos], axis=0))
            return new_pos, mask_pos, tri
    tri.add_points(new_pos)
    return new_pos, mask_pos, tri


class _GridData(object):
    """Unstructured (x,y) data interpolator.

    This class allows optimized interpolation by computing parameters
    for a fixed set of true points, and allowing the values at those points
    to be set independently.
    """

    def __init__(self, pos, extrapolate, origin, radii, border):
        # in principle this works in N dimensions, not just 2
        assert pos.ndim == 2 and pos.shape[1] == 2, pos.shape
        _validate_type(border, ('numeric', str), 'border')

        # check that border, if string, is correct
        if isinstance(border, str):
            _check_option('border', border, ('mean',), extra='when a string')

        # Adding points outside the extremes helps the interpolators
        outer_pts, mask_pts, tri = _get_extra_points(
            pos, extrapolate, origin, radii)
        self.n_extra = outer_pts.shape[0]
        self.mask_pts = mask_pts
        self.border = border
        self.tri = tri

    def set_values(self, v):
        """Set the values at interpolation points."""
        # Rbf with thin-plate is what we used to use, but it's slower and
        # looks about the same:
        #
        #     zi = Rbf(x, y, v, function='multiquadric', smooth=0)(xi, yi)
        #
        # Eventually we could also do set_values with this class if we want,
        # see scipy/interpolate/rbf.py, especially the self.nodes one-liner.
        from scipy.interpolate import CloughTocher2DInterpolator

        if isinstance(self.border, str):
            # we've already checked that border = 'mean'
            n_points = v.shape[0]
            v_extra = np.zeros(self.n_extra)
            indices, indptr = self.tri.vertex_neighbor_vertices
            rng = range(n_points, n_points + self.n_extra)
            used = np.zeros(len(rng), bool)
            for idx, extra_idx in enumerate(rng):
                ngb = indptr[indices[extra_idx]:indices[extra_idx + 1]]
                ngb = ngb[ngb < n_points]
                if len(ngb) > 0:
                    used[idx] = True
                    v_extra[idx] = v[ngb].mean()
            if not used.all() and used.any():
                # Eventually we might want to use the value of the nearest
                # point or something, but this case should hopefully be
                # rare so for now just use the average value of all extras
                v_extra[~used] = np.mean(v_extra[used])
        else:
            v_extra = np.full(self.n_extra, self.border, dtype=float)

        v = np.concatenate((v, v_extra))
        self.interpolator = CloughTocher2DInterpolator(self.tri, v)
        return self

    def set_locations(self, Xi, Yi):
        """Set locations for easier (delayed) calling."""
        self.Xi = Xi
        self.Yi = Yi
        return self

    def __call__(self, *args):
        """Evaluate the interpolator."""
        if len(args) == 0:
            args = [self.Xi, self.Yi]
        return self.interpolator(*args)


def _topomap_plot_sensors(pos_x, pos_y, sensors, ax):
    """Plot sensors."""
    if sensors is True:
        ax.scatter(pos_x, pos_y, s=0.25, marker='o',
                   edgecolor=['k'] * len(pos_x), facecolor='none')
    else:
        ax.plot(pos_x, pos_y, sensors)


def _get_pos_outlines(info, picks, sphere, to_sphere=True):
    ch_type = _get_ch_type(pick_info(_simplify_info(info), picks), None)
    orig_sphere = sphere
    sphere, clip_origin = _adjust_meg_sphere(sphere, info, ch_type)
    logger.debug('Generating pos outlines with sphere '
                 f'{sphere} from {orig_sphere} for {ch_type}')
    pos = _find_topomap_coords(
        info, picks, ignore_overlap=True, to_sphere=to_sphere,
        sphere=sphere)
    outlines = _make_head_outlines(sphere, pos, 'head', clip_origin)
    return pos, outlines


@fill_doc
def plot_topomap(data, pos, vmin=None, vmax=None, cmap=None, sensors=True,
                 res=64, axes=None, names=None, show_names=False, mask=None,
                 mask_params=None, outlines='head',
                 contours=6, image_interp='bilinear', show=True,
                 onselect=None, extrapolate=_EXTRAPOLATE_DEFAULT,
                 sphere=None, border=_BORDER_DEFAULT,
                 ch_type='eeg'):
    """Plot a topographic map as image.

    Parameters
    ----------
    data : array, shape (n_chan,)
        The data values to plot.
    pos : array, shape (n_chan, 2) | instance of Info
        Location information for the data points(/channels).
        If an array, for each data point, the x and y coordinates.
        If an Info object, it must contain only one data type and
        exactly ``len(data)`` data channels, and the x/y coordinates will
        be inferred from this Info object.
    vmin : float | callable | None
        The value specifying the lower bound of the color range.
        If None, and vmax is None, -vmax is used. Else np.min(data).
        If callable, the output equals vmin(data). Defaults to None.
    vmax : float | callable | None
        The value specifying the upper bound of the color range.
        If None, the maximum absolute value is used. If callable, the output
        equals vmax(data). Defaults to None.
    cmap : matplotlib colormap | None
        Colormap to use. If None, 'Reds' is used for all positive data,
        otherwise defaults to 'RdBu_r'.
    sensors : bool | str
        Add markers for sensor locations to the plot. Accepts matplotlib plot
        format string (e.g., 'r+' for red plusses). If True (default), circles
        will be used.
    res : int
        The resolution of the topomap image (n pixels along each side).
    axes : instance of Axes | None
        The axes to plot to. If None, the current axes will be used.
    names : list | None
        List of channel names. If None, channel names are not plotted.
    %(topomap_show_names)s
        If ``True``, a list of names must be provided (see ``names`` keyword).
    mask : ndarray of bool, shape (n_channels, n_times) | None
        The channels to be marked as significant at a given time point.
        Indices set to ``True`` will be considered. Defaults to None.
    mask_params : dict | None
        Additional plotting parameters for plotting significant sensors.
        Default (None) equals::

           dict(marker='o', markerfacecolor='w', markeredgecolor='k',
                linewidth=0, markersize=4)
    %(topomap_outlines)s
    contours : int | array of float
        The number of contour lines to draw. If 0, no contours will be drawn.
        If an array, the values represent the levels for the contours. The
        values are in µV for EEG, fT for magnetometers and fT/m for
        gradiometers. Defaults to 6.
    image_interp : str
        The image interpolation to be used. All matplotlib options are
        accepted.
    show : bool
        Show figure if True.
    onselect : callable | None
        Handle for a function that is called when the user selects a set of
        channels by rectangle selection (matplotlib ``RectangleSelector``). If
        None interactive selection is disabled. Defaults to None.
    %(topomap_extrapolate)s

        .. versionadded:: 0.18
    %(topomap_sphere)s
    %(topomap_border)s
    %(topomap_ch_type)s

    Returns
    -------
    im : matplotlib.image.AxesImage
        The interpolated data.
    cn : matplotlib.contour.ContourSet
        The fieldlines.
    """
    sphere = _check_sphere(sphere)
    return _plot_topomap(data, pos, vmin, vmax, cmap, sensors, res, axes,
                         names, show_names, mask, mask_params, outlines,
                         contours, image_interp, show,
                         onselect, extrapolate, sphere=sphere, border=border,
                         ch_type=ch_type)[:2]


def _setup_interp(pos, res, extrapolate, sphere, outlines, border):
    xlim = np.inf, -np.inf,
    ylim = np.inf, -np.inf,
    mask_ = np.c_[outlines['mask_pos']]
    clip_radius = outlines['clip_radius']
    clip_origin = outlines.get('clip_origin', (0., 0.))
    xmin, xmax = (np.min(np.r_[xlim[0],
                               mask_[:, 0],
                               clip_origin[0] - clip_radius[0]]),
                  np.max(np.r_[xlim[1],
                               mask_[:, 0],
                               clip_origin[0] + clip_radius[0]]))
    ymin, ymax = (np.min(np.r_[ylim[0],
                               mask_[:, 1],
                               clip_origin[1] - clip_radius[1]]),
                  np.max(np.r_[ylim[1],
                               mask_[:, 1],
                               clip_origin[1] + clip_radius[1]]))
    xi = np.linspace(xmin, xmax, res)
    yi = np.linspace(ymin, ymax, res)
    Xi, Yi = np.meshgrid(xi, yi)
    interp = _GridData(pos, extrapolate, clip_origin, clip_radius, border)
    extent = (xmin, xmax, ymin, ymax)
    return extent, Xi, Yi, interp


def _plot_topomap(data, pos, vmin=None, vmax=None, cmap=None, sensors=True,
                  res=64, axes=None, names=None, show_names=False, mask=None,
                  mask_params=None, outlines='head',
                  contours=6, image_interp='bilinear', show=True,
                  onselect=None, extrapolate=_EXTRAPOLATE_DEFAULT, sphere=None,
                  border=_BORDER_DEFAULT, ch_type='eeg'):
    import matplotlib.pyplot as plt
    from matplotlib.widgets import RectangleSelector
    data = np.asarray(data)
    logger.debug(f'Plotting topomap for {ch_type} data shape {data.shape}')

    if isinstance(pos, Info):  # infer pos from Info object
        picks = _pick_data_channels(pos, exclude=())  # pick only data channels
        pos = pick_info(pos, picks)

        # check if there is only 1 channel type, and n_chans matches the data
        ch_type = _get_channel_types(pos, unique=True)
        info_help = ("Pick Info with e.g. mne.pick_info and "
                     "mne.io.pick.channel_indices_by_type.")
        if len(ch_type) > 1:
            raise ValueError("Multiple channel types in Info structure. " +
                             info_help)
        elif len(pos["chs"]) != data.shape[0]:
            raise ValueError("Number of channels in the Info object (%s) and "
                             "the data array (%s) do not match. "
                             % (len(pos['chs']), data.shape[0]) + info_help)
        else:
            ch_type = ch_type.pop()

        if any(type_ in ch_type for type_ in ('planar', 'grad')):
            # deal with grad pairs
            picks = _pair_grad_sensors(pos, topomap_coords=False)
            pos = _find_topomap_coords(pos, picks=picks[::2], sphere=sphere)
            data, _ = _merge_ch_data(data, ch_type, [])
            data = data.reshape(-1)
        else:
            picks = list(range(data.shape[0]))
            pos = _find_topomap_coords(pos, picks=picks, sphere=sphere)

    _check_option('extrapolate', extrapolate, ('box', 'local', 'head', 'auto'))
    if extrapolate == 'auto':
        extrapolate = 'local' if ch_type in _MEG_CH_TYPES_SPLIT else 'head'

    if data.ndim > 1:
        raise ValueError("Data needs to be array of shape (n_sensors,); got "
                         "shape %s." % str(data.shape))

    # Give a helpful error message for common mistakes regarding the position
    # matrix.
    pos_help = ("Electrode positions should be specified as a 2D array with "
                "shape (n_channels, 2). Each row in this matrix contains the "
                "(x, y) position of an electrode.")
    if pos.ndim != 2:
        error = ("{ndim}D array supplied as electrode positions, where a 2D "
                 "array was expected").format(ndim=pos.ndim)
        raise ValueError(error + " " + pos_help)
    elif pos.shape[1] == 3:
        error = ("The supplied electrode positions matrix contains 3 columns. "
                 "Are you trying to specify XYZ coordinates? Perhaps the "
                 "mne.channels.create_eeg_layout function is useful for you.")
        raise ValueError(error + " " + pos_help)
    # No error is raised in case of pos.shape[1] == 4. In this case, it is
    # assumed the position matrix contains both (x, y) and (width, height)
    # values, such as Layout.pos.
    elif pos.shape[1] == 1 or pos.shape[1] > 4:
        raise ValueError(pos_help)
    pos = pos[:, :2]

    if len(data) != len(pos):
        raise ValueError("Data and pos need to be of same length. Got data of "
                         "length %s, pos of length %s" % (len(data), len(pos)))

    norm = min(data) >= 0
    vmin, vmax = _setup_vmin_vmax(data, vmin, vmax, norm)
    if cmap is None:
        cmap = 'Reds' if norm else 'RdBu_r'

    outlines = _make_head_outlines(sphere, pos, outlines, (0., 0.))
    assert isinstance(outlines, dict)

    ax = axes if axes else plt.gca()
    _prepare_topomap(pos, ax)

    _use_default_outlines = any(k.startswith('head') for k in outlines)
    mask_params = _handle_default('mask_params', mask_params)

    # find mask limits
    clip_radius = outlines['clip_radius']
    clip_origin = outlines.get('clip_origin', (0., 0.))
    extent, Xi, Yi, interp = _setup_interp(
        pos, res, extrapolate, sphere, outlines, border)
    interp.set_values(data)
    Zi = interp.set_locations(Xi, Yi)()

    # plot outline
    patch_ = None
    if 'patch' in outlines:
        patch_ = outlines['patch']
        patch_ = patch_() if callable(patch_) else patch_
        patch_.set_clip_on(False)
        ax.add_patch(patch_)
        ax.set_transform(ax.transAxes)
        ax.set_clip_path(patch_)
    if _use_default_outlines:
        from matplotlib import patches
        if extrapolate == 'local':
            patch_ = patches.Polygon(
                interp.mask_pts, clip_on=True, transform=ax.transData)
        else:
            patch_ = patches.Ellipse(
                clip_origin, 2 * clip_radius[0], 2 * clip_radius[1],
                clip_on=True, transform=ax.transData)

    # plot interpolated map
    im = ax.imshow(Zi, cmap=cmap, vmin=vmin, vmax=vmax, origin='lower',
                   aspect='equal', extent=extent,
                   interpolation=image_interp)

    # gh-1432 had a workaround for no contours here, but we'll remove it
    # because mpl has probably fixed it
    linewidth = mask_params['markeredgewidth']
    cont = True
    if isinstance(contours, (np.ndarray, list)):
        pass
    elif contours == 0 or ((Zi == Zi[0, 0]) | np.isnan(Zi)).all():
        cont = None  # can't make contours for constant-valued functions
    if cont:
        with warnings.catch_warnings(record=True):
            warnings.simplefilter('ignore')
            cont = ax.contour(Xi, Yi, Zi, contours, colors='k',
                              linewidths=linewidth / 2.)

    if patch_ is not None:
        im.set_clip_path(patch_)
        if cont is not None:
            for col in cont.collections:
                col.set_clip_path(patch_)

    pos_x, pos_y = pos.T
    if sensors is not False and mask is None:
        _topomap_plot_sensors(pos_x, pos_y, sensors=sensors, ax=ax)
    elif sensors and mask is not None:
        idx = np.where(mask)[0]
        ax.plot(pos_x[idx], pos_y[idx], **mask_params)
        idx = np.where(~mask)[0]
        _topomap_plot_sensors(pos_x[idx], pos_y[idx], sensors=sensors, ax=ax)
    elif not sensors and mask is not None:
        idx = np.where(mask)[0]
        ax.plot(pos_x[idx], pos_y[idx], **mask_params)

    if isinstance(outlines, dict):
        _draw_outlines(ax, outlines)

    if show_names:
        if names is None:
            raise ValueError("To show names, a list of names must be provided"
                             " (see `names` keyword).")
        if show_names is True:
            def _show_names(x):
                return x
        else:
            _show_names = show_names
        show_idx = np.arange(len(names)) if mask is None else np.where(mask)[0]
        for ii, (p, ch_id) in enumerate(zip(pos, names)):
            if ii not in show_idx:
                continue
            ch_id = _show_names(ch_id)
            ax.text(p[0], p[1], ch_id, horizontalalignment='center',
                    verticalalignment='center', size='x-small')

    plt.subplots_adjust(top=.95)

    if onselect is not None:
        lim = ax.dataLim
        x0, y0, width, height = lim.x0, lim.y0, lim.width, lim.height
        ax.RS = RectangleSelector(ax, onselect=onselect)
        ax.set(xlim=[x0, x0 + width], ylim=[y0, y0 + height])
    plt_show(show)
    return im, cont, interp


def _plot_ica_topomap(ica, idx=0, ch_type=None, res=64,
                      vmin=None, vmax=None, cmap='RdBu_r', colorbar=False,
                      title=None, show=True, outlines='head', contours=6,
                      image_interp='bilinear', axes=None,
                      sensors=True, allow_ref_meg=False,
                      extrapolate=_EXTRAPOLATE_DEFAULT,
                      sphere=None, border=_BORDER_DEFAULT):
    """Plot single ica map to axes."""
    from matplotlib.axes import Axes

    if ica.info is None:
        raise RuntimeError('The ICA\'s measurement info is missing. Please '
                           'fit the ICA or add the corresponding info object.')
    sphere = _check_sphere(sphere, ica.info)
    if not isinstance(axes, Axes):
        raise ValueError('axis has to be an instance of matplotlib Axes, '
                         'got %s instead.' % type(axes))
    ch_type = _get_ch_type(ica, ch_type, allow_ref_meg=ica.allow_ref_meg)
    if ch_type == "ref_meg":
        logger.info("Cannot produce topographies for MEG reference channels.")
        return

    data = ica.get_components()[:, idx]
    data_picks, pos, merge_channels, names, _, sphere, clip_origin = \
        _prepare_topomap_plot(ica, ch_type, sphere=sphere)
    data = data[data_picks]
    outlines = _make_head_outlines(sphere, pos, outlines, clip_origin)

    if merge_channels:
        data, names = _merge_ch_data(data, ch_type, names)

    axes.set_title(ica._ica_names[idx], fontsize=12)
    vmin_, vmax_ = _setup_vmin_vmax(data, vmin, vmax)
    im = plot_topomap(
        data.ravel(), pos, vmin=vmin_, vmax=vmax_, res=res, axes=axes,
        cmap=cmap, outlines=outlines, contours=contours, sensors=sensors,
        image_interp=image_interp, show=show, extrapolate=extrapolate,
        sphere=sphere, border=border)[0]
    if colorbar:
        cbar, cax = _add_colorbar(axes, im, cmap, pad=.05, title="AU",
                                  format='%3.2f')
        cbar.ax.tick_params(labelsize=12)
        cbar.set_ticks((vmin_, vmax_))
    _hide_frame(axes)


@fill_doc
def plot_ica_components(ica, picks=None, ch_type=None, res=64,
                        vmin=None, vmax=None, cmap='RdBu_r',
                        sensors=True, colorbar=False, title=None,
                        show=True, outlines='head', contours=6,
                        image_interp='bilinear',
                        inst=None, plot_std=True, topomap_args=None,
                        image_args=None, psd_args=None, reject='auto',
                        sphere=None):
    """Project mixing matrix on interpolated sensor topography.

    Parameters
    ----------
    ica : instance of mne.preprocessing.ICA
        The ICA solution.
    %(picks_all)s
        If None all are plotted in batches of 20.
    ch_type : 'mag' | 'grad' | 'planar1' | 'planar2' | 'eeg' | None
        The channel type to plot. For 'grad', the gradiometers are
        collected in pairs and the RMS for each pair is plotted.
        If None, then channels are chosen in the order given above.
    res : int
        The resolution of the topomap image (n pixels along each side).
    vmin : float | callable | None
        The value specifying the lower bound of the color range.
        If None, and vmax is None, -vmax is used. Else np.min(data).
        If callable, the output equals vmin(data). Defaults to None.
    vmax : float | callable | None
        The value specifying the upper bound of the color range.
        If None, the maximum absolute value is used. If callable, the output
        equals vmax(data). Defaults to None.
    cmap : matplotlib colormap | (colormap, bool) | 'interactive' | None
        Colormap to use. If tuple, the first value indicates the colormap to
        use and the second value is a boolean defining interactivity. In
        interactive mode the colors are adjustable by clicking and dragging the
        colorbar with left and right mouse button. Left mouse button moves the
        scale up and down and right mouse button adjusts the range. Hitting
        space bar resets the range. Up and down arrows can be used to change
        the colormap. If None, 'Reds' is used for all positive data,
        otherwise defaults to 'RdBu_r'. If 'interactive', translates to
        (None, True). Defaults to 'RdBu_r'.

        .. warning::  Interactive mode works smoothly only for a small amount
                      of topomaps.
    sensors : bool | str
        Add markers for sensor locations to the plot. Accepts matplotlib
        plot format string (e.g., 'r+' for red plusses). If True (default),
        circles  will be used.
    colorbar : bool
        Plot a colorbar.
    title : str | None
        Title to use.
    show : bool
        Show figure if True.
    %(topomap_outlines)s
    contours : int | array of float
        The number of contour lines to draw. If 0, no contours will be drawn.
        When an integer, matplotlib ticker locator is used to find suitable
        values for the contour thresholds (may sometimes be inaccurate, use
        array for accuracy). If an array, the values represent the levels for
        the contours. Defaults to 6.
    image_interp : str
        The image interpolation to be used. All matplotlib options are
        accepted.
    inst : Raw | Epochs | None
        To be able to see component properties after clicking on component
        topomap you need to pass relevant data - instances of Raw or Epochs
        (for example the data that ICA was trained on). This takes effect
        only when running matplotlib in interactive mode.
    plot_std : bool | float
        Whether to plot standard deviation in ERP/ERF and spectrum plots.
        Defaults to True, which plots one standard deviation above/below.
        If set to float allows to control how many standard deviations are
        plotted. For example 2.5 will plot 2.5 standard deviation above/below.
    topomap_args : dict | None
        Dictionary of arguments to ``plot_topomap``. If None, doesn't pass any
        additional arguments. Defaults to None.
    image_args : dict | None
        Dictionary of arguments to ``plot_epochs_image``. If None, doesn't pass
        any additional arguments. Defaults to None.
    psd_args : dict | None
        Dictionary of arguments to ``psd_multitaper``. If None, doesn't pass
        any additional arguments. Defaults to None.
    reject : 'auto' | dict | None
        Allows to specify rejection parameters used to drop epochs
        (or segments if continuous signal is passed as inst).
        If None, no rejection is applied. The default is 'auto',
        which applies the rejection parameters used when fitting
        the ICA object.
    %(topomap_sphere_auto)s

    Returns
    -------
    fig : instance of matplotlib.figure.Figure or list
        The figure object(s).

    Notes
    -----
    When run in interactive mode, ``plot_ica_components`` allows to reject
    components by clicking on their title label. The state of each component
    is indicated by its label color (gray: rejected; black: retained). It is
    also possible to open component properties by clicking on the component
    topomap (this option is only available when the ``inst`` argument is
    supplied).
    """
    from ..io import BaseRaw
    from ..epochs import BaseEpochs

    if ica.info is None:
        raise RuntimeError('The ICA\'s measurement info is missing. Please '
                           'fit the ICA or add the corresponding info object.')

    topomap_args = dict() if topomap_args is None else topomap_args
    topomap_args = copy.copy(topomap_args)
    if 'sphere' not in topomap_args:
        topomap_args['sphere'] = sphere
    if picks is None:  # plot components by sets of 20
        ch_type = _get_ch_type(ica, ch_type)
        n_components = ica.mixing_matrix_.shape[1]
        p = 20
        figs = []
        for k in range(0, n_components, p):
            picks = range(k, min(k + p, n_components))
            fig = plot_ica_components(ica, picks=picks, ch_type=ch_type,
                                      res=res, vmax=vmax,
                                      cmap=cmap, sensors=sensors,
                                      colorbar=colorbar, title=title,
                                      show=show, outlines=outlines,
                                      contours=contours,
                                      image_interp=image_interp, inst=inst,
                                      plot_std=plot_std,
                                      topomap_args=topomap_args,
                                      image_args=image_args,
                                      psd_args=psd_args, reject=reject,
                                      sphere=sphere)
            figs.append(fig)
        return figs
    else:
        picks = _picks_to_idx(ica.info, picks)
    ch_type = _get_ch_type(ica, ch_type)

    cmap = _setup_cmap(cmap, n_axes=len(picks))
    data = np.dot(ica.mixing_matrix_[:, picks].T,
                  ica.pca_components_[:ica.n_components_])

    data_picks, pos, merge_channels, names, _, sphere, clip_origin = \
        _prepare_topomap_plot(ica, ch_type, sphere=sphere)
    outlines = _make_head_outlines(sphere, pos, outlines, clip_origin)

    data = np.atleast_2d(data)
    data = data[:, data_picks]

    # prepare data for iteration
    fig, axes, _, _ = _prepare_trellis(len(data), ncols=5)
    if title is None:
        title = 'ICA components'
    fig.suptitle(title)

    titles = list()
    for ii, data_, ax in zip(picks, data, axes):
        kwargs = dict(color='gray') if ii in ica.exclude else dict()
        titles.append(ax.set_title(ica._ica_names[ii], fontsize=12, **kwargs))
        if merge_channels:
            data_, names_ = _merge_ch_data(data_, ch_type, names.copy())
        vmin_, vmax_ = _setup_vmin_vmax(data_, vmin, vmax)
        im = plot_topomap(
            data_.flatten(), pos, vmin=vmin_, vmax=vmax_, res=res, axes=ax,
            cmap=cmap[0], outlines=outlines, contours=contours,
            image_interp=image_interp, show=False, sensors=sensors)[0]
        im.axes.set_label(ica._ica_names[ii])
        if colorbar:
            cbar, cax = _add_colorbar(ax, im, cmap, title="AU",
                                      side="right", pad=.05, format='%3.2f')
            cbar.ax.tick_params(labelsize=12)
            cbar.set_ticks((vmin_, vmax_))
        _hide_frame(ax)
    del pos
    tight_layout(fig=fig)
    fig.subplots_adjust(top=0.88, bottom=0.)
    fig.canvas.draw()

    # add title selection interactivity
    def onclick_title(event, ica=ica, titles=titles):
        # check if any title was pressed
        title_pressed = None
        for title in titles:
            if title.contains(event)[0]:
                title_pressed = title
                break
        # title was pressed -> identify the IC
        if title_pressed is not None:
            label = title_pressed.get_text()
            ic = int(label[-3:])
            # add or remove IC from exclude depending on current state
            if ic in ica.exclude:
                ica.exclude.remove(ic)
                title_pressed.set_color('k')
            else:
                ica.exclude.append(ic)
                title_pressed.set_color('gray')
            fig.canvas.draw()
    fig.canvas.mpl_connect('button_press_event', onclick_title)

    # add plot_properties interactivity only if inst was passed
    if isinstance(inst, (BaseRaw, BaseEpochs)):
        def onclick_topo(event, ica=ica, inst=inst):
            # check which component to plot
            if event.inaxes is not None:
                label = event.inaxes.get_label()
                if label.startswith('ICA'):
                    ic = int(label[-3:])
                    ica.plot_properties(inst, picks=ic, show=True,
                                        plot_std=plot_std,
                                        topomap_args=topomap_args,
                                        image_args=image_args,
                                        psd_args=psd_args, reject=reject)
        fig.canvas.mpl_connect('button_press_event', onclick_topo)

    plt_show(show)
    return fig


@fill_doc
def plot_tfr_topomap(tfr, tmin=None, tmax=None, fmin=None, fmax=None,
                     ch_type=None, baseline=None, mode='mean',
                     vmin=None, vmax=None, cmap=None, sensors=True,
                     colorbar=True, unit=None, res=64, size=2,
                     cbar_fmt='%1.1e', show_names=False, title=None,
                     axes=None, show=True, outlines='head',
                     contours=6, sphere=None):
    """Plot topographic maps of specific time-frequency intervals of TFR data.

    Parameters
    ----------
    tfr : AverageTFR
        The AverageTFR object.
    tmin : None | float
        The first time instant to display. If None the first time point
        available is used.
    tmax : None | float
        The last time instant to display. If None the last time point available
        is used.
    fmin : None | float
        The first frequency to display. If None the first frequency available
        is used.
    fmax : None | float
        The last frequency to display. If None the last frequency available is
        used.
    ch_type : 'mag' | 'grad' | 'planar1' | 'planar2' | 'eeg' | None
        The channel type to plot. For 'grad', the gradiometers are collected in
        pairs and the mean for each pair is plotted. If None, then channels are
        chosen in the order given above.
    baseline : tuple or list of length 2
        The time interval to apply rescaling / baseline correction. If None do
        not apply it. If baseline is (a, b) the interval is between "a (s)" and
        "b (s)". If a is None the beginning of the data is used and if b is
        None then b is set to the end of the interval. If baseline is equal to
        (None, None) the whole time interval is used.
    mode : 'mean' | 'ratio' | 'logratio' | 'percent' | 'zscore' | 'zlogratio' | None
        Perform baseline correction by

          - subtracting the mean baseline power ('mean')
          - dividing by the mean baseline power ('ratio')
          - dividing by the mean baseline power and taking the log ('logratio')
          - subtracting the mean baseline power followed by dividing by the
            mean baseline power ('percent')
          - subtracting the mean baseline power and dividing by the standard
            deviation of the baseline power ('zscore')
          - dividing by the mean baseline power, taking the log, and dividing
            by the standard deviation of the baseline power ('zlogratio')

        If None no baseline correction is applied.
    vmin : float | callable | None
        The value specifying the lower bound of the color range.
        If None, and vmax is None, -vmax is used. Else np.min(data) or in case
        data contains only positive values 0. If callable, the output equals
        vmin(data). Defaults to None.
    vmax : float | callable | None
        The value specifying the upper bound of the color range. If None, the
        maximum value is used. If callable, the output equals vmax(data).
        Defaults to None.
    cmap : matplotlib colormap | (colormap, bool) | 'interactive' | None
        Colormap to use. If tuple, the first value indicates the colormap to
        use and the second value is a boolean defining interactivity. In
        interactive mode the colors are adjustable by clicking and dragging the
        colorbar with left and right mouse button. Left mouse button moves the
        scale up and down and right mouse button adjusts the range. Hitting
        space bar resets the range. Up and down arrows can be used to change
        the colormap. If None (default), 'Reds' is used for all positive data,
        otherwise defaults to 'RdBu_r'. If 'interactive', translates to
        (None, True).
    sensors : bool | str
        Add markers for sensor locations to the plot. Accepts matplotlib plot
        format string (e.g., 'r+'). If True (default), circles will be used.
    colorbar : bool
        Plot a colorbar.
    unit : str | None
        The unit of the channel type used for colorbar labels.
    res : int
        The resolution of the topomap image (n pixels along each side).
    size : float
        Side length per topomap in inches (only applies when plotting multiple
        topomaps at a time).
    cbar_fmt : str
        String format for colorbar values.
    %(topomap_show_names)s
    title : str | None
        Plot title. If None (default), no title is displayed.
    axes : instance of Axes | None
        The axes to plot to. If None the axes is defined automatically.
    show : bool
        Show figure if True.
    %(topomap_outlines)s
    contours : int | array of float
        The number of contour lines to draw. If 0, no contours will be drawn.
        When an integer, matplotlib ticker locator is used to find suitable
        values for the contour thresholds (may sometimes be inaccurate, use
        array for accuracy). If an array, the values represent the levels for
        the contours. If colorbar=True, the ticks in colorbar correspond to the
        contour levels. Defaults to 6.
    %(topomap_sphere_auto)s

    Returns
    -------
    fig : matplotlib.figure.Figure
        The figure containing the topography.
    """  # noqa: E501
    import matplotlib.pyplot as plt
    ch_type = _get_ch_type(tfr, ch_type)

    picks, pos, merge_channels, names, _, sphere, clip_origin = \
        _prepare_topomap_plot(tfr, ch_type, sphere=sphere)
    outlines = _make_head_outlines(sphere, pos, outlines, clip_origin)

    if not show_names:
        names = None

    data = tfr.data[picks, :, :]

    # merging grads before rescaling makes ERDs visible
    if merge_channels:
        data, names = _merge_ch_data(data, ch_type, names, method='mean')

    data = rescale(data, tfr.times, baseline, mode, copy=True)

    # crop time
    itmin, itmax = None, None
    idx = np.where(_time_mask(tfr.times, tmin, tmax))[0]
    if tmin is not None:
        itmin = idx[0]
    if tmax is not None:
        itmax = idx[-1] + 1

    # crop freqs
    ifmin, ifmax = None, None
    idx = np.where(_time_mask(tfr.freqs, fmin, fmax))[0]
    if fmin is not None:
        ifmin = idx[0]
    if fmax is not None:
        ifmax = idx[-1] + 1

    data = data[:, ifmin:ifmax, itmin:itmax]
    data = np.mean(np.mean(data, axis=2), axis=1)[:, np.newaxis]

    norm = False if np.min(data) < 0 else True
    vmin, vmax = _setup_vmin_vmax(data, vmin, vmax, norm)
    cmap = _setup_cmap(cmap, norm=norm)

    axes = plt.subplots(figsize=(size, size))[1] if axes is None else axes
    fig = axes.figure

    _hide_frame(axes)

    locator = None
    if not isinstance(contours, (list, np.ndarray)):
        locator, contours = _set_contour_locator(vmin, vmax, contours)

    if title is not None:
        axes.set_title(title)
    fig_wrapper = list()
    selection_callback = partial(_onselect, tfr=tfr, pos=pos, ch_type=ch_type,
                                 itmin=itmin, itmax=itmax, ifmin=ifmin,
                                 ifmax=ifmax, cmap=cmap[0], fig=fig_wrapper)

    if not isinstance(contours, (list, np.ndarray)):
        _, contours = _set_contour_locator(vmin, vmax, contours)

    im, _ = plot_topomap(data[:, 0], pos, vmin=vmin, vmax=vmax,
                         axes=axes, cmap=cmap[0], image_interp='bilinear',
                         contours=contours, names=names, show_names=show_names,
                         show=False, onselect=selection_callback,
                         sensors=sensors, res=res, ch_type=ch_type,
                         outlines=outlines, sphere=sphere)

    if colorbar:
        from matplotlib import ticker
        unit = _handle_default('units', unit)['misc']
        cbar, cax = _add_colorbar(axes, im, cmap, title=unit, format=cbar_fmt)
        if locator is None:
            locator = ticker.MaxNLocator(nbins=5)
        cbar.locator = locator
        cbar.update_ticks()
        cbar.ax.tick_params(labelsize=12)

    plt_show(show)
    return fig


@fill_doc
def plot_evoked_topomap(evoked, times="auto", ch_type=None,
                        vmin=None, vmax=None, cmap=None, sensors=True,
                        colorbar=True, scalings=None,
                        units=None, res=64, size=1, cbar_fmt='%3.1f',
                        time_unit='s', time_format=None, proj=False,
                        show=True, show_names=False, title=None, mask=None,
                        mask_params=None, outlines='head', contours=6,
                        image_interp='bilinear', average=None,
                        axes=None, extrapolate=_EXTRAPOLATE_DEFAULT,
                        sphere=None, border=_BORDER_DEFAULT,
                        nrows=1, ncols='auto'):
    """Plot topographic maps of specific time points of evoked data.

    Parameters
    ----------
    evoked : Evoked
        The Evoked object.
    times : float | array of float | "auto" | "peaks" | "interactive"
        The time point(s) to plot. If "auto", the number of ``axes`` determines
        the amount of time point(s). If ``axes`` is also None, at most 10
        topographies will be shown with a regular time spacing between the
        first and last time instant. If "peaks", finds time points
        automatically by checking for local maxima in global field power. If
        "interactive", the time can be set interactively at run-time by using a
        slider.
    %(topomap_ch_type)s
    %(topomap_vmin_vmax)s
    %(topomap_cmap)s
    %(topomap_sensors)s
    %(topomap_colorbar)s
    %(topomap_scalings)s
    %(topomap_units)s
    %(topomap_res)s
    %(topomap_size)s
    %(topomap_cbar_fmt)s
    time_unit : str
        The units for the time axis, can be "ms" or "s" (default).

        .. versionadded:: 0.16
    time_format : str | None
        String format for topomap values. Defaults (None) to "%%01d ms" if
        ``time_unit='ms'``, "%%0.3f s" if ``time_unit='s'``, and
        "%%g" otherwise. Can be an empty string to omit the time label.
    %(plot_proj)s
    %(show)s
    %(topomap_show_names)s
    %(title_None)s
    %(topomap_mask)s
    %(topomap_mask_params)s
    %(topomap_outlines)s
    %(topomap_contours)s
    %(topomap_image_interp)s
    %(topomap_average)s
    %(topomap_axes)s
    %(topomap_extrapolate)s

        .. versionadded:: 0.18
    %(topomap_sphere_auto)s
    %(topomap_border)s
    nrows : int | 'auto'
        The number of rows of topographies to plot. Defaults to 1. If 'auto',
        obtains the number of rows depending on the amount of times to plot
        and the number of cols. Not valid when times == 'interactive'.

        .. versionadded:: 0.20
    ncols : int | 'auto'
        The number of columns of topographies to plot. If 'auto' (default),
        obtains the number of columns depending on the amount of times to plot
        and the number of rows. Not valid when times == 'interactive'.

        .. versionadded:: 0.20

    Returns
    -------
    fig : instance of matplotlib.figure.Figure
       The figure.

    Notes
    -----
    When existing ``axes`` are provided and ``colorbar=True``, note that the
    colorbar scale will only accurately reflect topomaps that are generated in
    the same call as the colorbar. Note also that the colorbar will not be
    resized automatically when ``axes`` are provided; use matplotlib's
    :meth:`axes.set_position() <matplotlib.axes.Axes.set_position>` method or
    :doc:`gridspec <matplotlib:tutorials/intermediate/gridspec>` interface to
    adjust the colorbar size yourself.
    """
    import matplotlib.pyplot as plt
    from matplotlib.gridspec import GridSpec
    from matplotlib.widgets import Slider
    from ..evoked import Evoked

    _validate_type(evoked, Evoked, 'evoked')
    evoked = evoked.copy()  # make a copy, since we'll be picking
    ch_type = _get_ch_type(evoked, ch_type)
    # deprecation
    if colorbar is None:
        colorbar = True
        warn('colorbar=None is deprecated and will be removed in version 0.22;'
             ' use colorbar=True (or False) instead.', DeprecationWarning)
    # time units / formatting
    time_unit, _ = _check_time_unit(time_unit, evoked.times)
    scaling_time = 1. if time_unit == 's' else 1e3
    _validate_type(time_format, (None, str), 'time_format')
    if time_format is None:
        time_format = '%0.3f s' if time_unit == 's' else '%01d ms'
    del time_unit
    # mask_params defaults
    mask_params = _handle_default('mask_params', mask_params)
    mask_params['markersize'] *= size / 2.
    mask_params['markeredgewidth'] *= size / 2.
    # setup various parameters, and prepare outlines
    picks, pos, merge_channels, names, ch_type, sphere, clip_origin = \
        _prepare_topomap_plot(evoked, ch_type, sphere=sphere)
    outlines = _make_head_outlines(sphere, pos, outlines, clip_origin)
    # check interactive
    axes_given = axes is not None
    interactive = isinstance(times, str) and times == 'interactive'
    if interactive and axes_given:
        raise ValueError("User-provided axes not allowed when "
                         "times='interactive'.")
    # units, scalings
    key = 'grad' if ch_type.startswith('planar') else ch_type
    scaling = _handle_default('scalings', scalings)[key]
    unit = _handle_default('units', units)[key]
    # ch_names (required for NIRS)
    ch_names = names
    if not show_names:
        names = None
    # apply projections before picking. NOTE: the `if proj is True`
    # anti-pattern is needed here to exclude proj='interactive'
    _check_option('proj', proj, (True, False, 'interactive', 'reconstruct'))
    if proj is True and not evoked.proj:
        evoked.apply_proj()
    elif proj == 'reconstruct':
        evoked._reconstruct_proj()
    data = evoked.data

    # remove compensation matrices (safe: only plotting & already made copy)
    evoked.info['comps'] = []
    evoked = evoked._pick_drop_channels(picks)
    # determine which times to plot
    if isinstance(axes, plt.Axes):
        axes = [axes]
    n_peaks = len(axes) - int(colorbar) if axes_given else None
    times = _process_times(evoked, times, n_peaks)
    n_times = len(times)
    space = 1 / (2. * evoked.info['sfreq'])
    if (max(times) > max(evoked.times) + space or
            min(times) < min(evoked.times) - space):
        raise ValueError(f'Times should be between {evoked.times[0]:0.3} and '
                         f'{evoked.times[-1]:0.3}.')
    # create axes
    want_axes = n_times + int(colorbar)
    if interactive:
        height_ratios = [5, 1]
        nrows = 2
        ncols = want_axes
        width = size * ncols
        height = size + max(0, 0.1 * (4 - size)) + bool(title) * 0.5
        fig = figure_nobar(figsize=(width * 1.5, height * 1.5))
        g_kwargs = {'left': 0.2, 'right': 0.8, 'bottom': 0.05, 'top': 0.9}
        gs = GridSpec(nrows, ncols, height_ratios=height_ratios, **g_kwargs)
        axes = []
        for ax_idx in range(n_times):
            axes.append(plt.subplot(gs[0, ax_idx]))
    elif axes is None:
        fig, axes, ncols, nrows = _prepare_trellis(
            n_times, ncols=ncols, nrows=nrows, title=title,
            colorbar=colorbar, size=size)
    else:
        nrows, ncols = None, None  # Deactivate ncols when axes were passed
        fig = axes[0].get_figure()
        # check: enough space for colorbar?
        if len(axes) != want_axes:
            cbar_err = ' plus one for the colorbar' if colorbar else ''
            raise RuntimeError(f'You must provide {want_axes} axes (one for '
                               f'each time{cbar_err}), got {len(axes)}.')
    # figure margins
    side_margin = plt.rcParams['figure.subplot.wspace'] / (2 * want_axes)
    top_margin = max((0.05 if title is None else 0.25), .2 / size)
    fig.subplots_adjust(left=side_margin, right=1 - side_margin, bottom=0,
                        top=1 - top_margin)
    # find first index that's >= (to rounding error) to each time point
    time_idx = [np.where(_time_mask(evoked.times, tmin=t, tmax=None,
                                    sfreq=evoked.info['sfreq']))[0][0]
                for t in times]
    # do averaging if requested
    avg_err = '"average" must be `None` or a positive number of seconds'
    if average is None:
        data = data[np.ix_(picks, time_idx)]
    elif not _is_numeric(average):
        raise TypeError(f'{avg_err}; got type {type(average)}.')
    elif average <= 0:
        raise ValueError(f'{avg_err}; got {average}.')
    else:
        data_ = np.zeros((len(picks), len(time_idx)))
        ave_time = average / 2.
        iter_times = evoked.times[time_idx]
        for ii, (idx, tmin_, tmax_) in enumerate(zip(time_idx,
                                                     iter_times - ave_time,
                                                     iter_times + ave_time)):
            my_range = (tmin_ < evoked.times) & (evoked.times < tmax_)
            data_[:, ii] = data[picks][:, my_range].mean(-1)
        data = data_
    # apply scalings and merge channels
    data *= scaling
    if merge_channels:
        data, ch_names = _merge_ch_data(data, ch_type, ch_names)
        if ch_type in _fnirs_types:
            merge_channels = False
    # apply mask if requested
    if mask is not None:
        if ch_type == 'grad':
            mask_ = (mask[np.ix_(picks[::2], time_idx)] |
                     mask[np.ix_(picks[1::2], time_idx)])
        else:  # mag, eeg, planar1, planar2
            mask_ = mask[np.ix_(picks, time_idx)]
    # set up colormap
    vlims = [_setup_vmin_vmax(data[:, i], vmin, vmax, norm=merge_channels)
             for i in range(n_times)]
    vmin = np.min(vlims)
    vmax = np.max(vlims)
    cmap = _setup_cmap(cmap, n_axes=n_times, norm=vmin >= 0)
    # set up contours
    if not isinstance(contours, (list, np.ndarray)):
        _, contours = _set_contour_locator(vmin, vmax, contours)
    # prepare for main loop over times
    kwargs = dict(vmin=vmin, vmax=vmax, sensors=sensors, res=res, names=names,
                  show_names=show_names, cmap=cmap[0], mask_params=mask_params,
                  outlines=outlines, contours=contours,
                  image_interp=image_interp, show=False,
                  extrapolate=extrapolate, sphere=sphere, border=border,
                  ch_type=ch_type)
    images, contours_ = [], []
    # loop over times
    for idx, time in enumerate(times):
        adjust_for_cbar = colorbar and ncols is not None and idx >= ncols - 1
        ax_idx = idx + 1 if adjust_for_cbar else idx
        tp, cn, interp = _plot_topomap(
            data[:, idx], pos, axes=axes[ax_idx],
            mask=mask_[:, idx] if mask is not None else None, **kwargs)

        images.append(tp)
        if cn is not None:
            contours_.append(cn)
        if time_format != '':
            axes[ax_idx].set_title(time_format % (time * scaling_time))

    if interactive:
        axes.append(plt.subplot(gs[1, :-1]))
        slider = Slider(axes[-1], 'Time', evoked.times[0], evoked.times[-1],
                        times[0], valfmt='%1.2fs')
        slider.vline.remove()  # remove initial point indicator
        func = _merge_ch_data if merge_channels else lambda x: x
        changed_callback = partial(_slider_changed, ax=axes[0],
                                   data=evoked.data, times=evoked.times,
                                   pos=pos, scaling=scaling, func=func,
                                   time_format=time_format,
                                   scaling_time=scaling_time, kwargs=kwargs)
        slider.on_changed(changed_callback)
        ts = np.tile(evoked.times, len(evoked.data)).reshape(evoked.data.shape)
        axes[-1].plot(ts, evoked.data, color='k')
        axes[-1].slider = slider
    if title is not None:
        plt.suptitle(title, verticalalignment='top', size='x-large')

    if colorbar:
        if interactive:
            cax = plt.subplot(gs[0, -1])
            _resize_cbar(cax, ncols, size)
        elif nrows is None or ncols is None:
            # axes were given by the user, so don't resize the colorbar
            cax = axes[-1]
        else:  # use the entire last column
            cax = axes[ncols - 1]
            _resize_cbar(cax, ncols, size)

        if unit is not None:
            cax.set_title(unit)
        cbar = fig.colorbar(images[-1], ax=cax, cax=cax, format=cbar_fmt)
        if cn is not None:
            cbar.set_ticks(contours)
        cbar.ax.tick_params(labelsize=7)
        if cmap[1]:
            for im in images:
                im.axes.CB = DraggableColorbar(cbar, im)

    if proj == 'interactive':
        _check_delayed_ssp(evoked)
        params = dict(
            evoked=evoked, fig=fig, projs=evoked.info['projs'], picks=picks,
            images=images, contours_=contours_, pos=pos, time_idx=time_idx,
            res=res, plot_update_proj_callback=_plot_update_evoked_topomap,
            merge_channels=merge_channels, scale=scaling, axes=axes,
            contours=contours, interp=interp, extrapolate=extrapolate)
        _draw_proj_checkbox(None, params)

    plt_show(show, block=False)
    if axes_given:
        fig.canvas.draw()
    return fig


def _resize_cbar(cax, n_fig_axes, size=1):
    """Resize colorbar."""
    cpos = cax.get_position()
    if size <= 1:
        cpos.x0 = 1 - (0.7 + 0.1 / size) / n_fig_axes
    cpos.x1 = cpos.x0 + 0.1 / n_fig_axes
    cpos.y0 = 0.2
    cpos.y1 = 0.7
    cax.set_position(cpos)


def _slider_changed(val, ax, data, times, pos, scaling, func, time_format,
                    scaling_time, kwargs):
    """Handle selection in interactive topomap."""
    idx = np.argmin(np.abs(times - val))
    data = func(data[:, idx]).ravel() * scaling
    ax.clear()
    im, _ = plot_topomap(data, pos, axes=ax, **kwargs)
    if hasattr(ax, 'CB'):
        ax.CB.mappable = im
        _resize_cbar(ax.CB.cbar.ax, 2)
    if time_format is not None:
        ax.set_title(time_format % (val * scaling_time))


def _plot_topomap_multi_cbar(data, pos, ax, title=None, unit=None, vmin=None,
                             vmax=None, cmap=None, outlines='head',
                             colorbar=False, cbar_fmt='%3.3f',
                             sphere=None, ch_type='eeg'):
    """Plot topomap multi cbar."""
    _hide_frame(ax)
    vmin = np.min(data) if vmin is None else vmin
    vmax = np.max(data) if vmax is None else vmax
    # this definition of "norm" allows non-diverging colormap for cases where
    # min & vmax are both negative (e.g., when they are power in dB)
    signs = np.sign([vmin, vmax])
    norm = len(set(signs)) == 1 or np.any(signs == 0)

    cmap = _setup_cmap(cmap, norm=norm)
    if title is not None:
        ax.set_title(title, fontsize=10)
    im, _ = plot_topomap(data, pos, vmin=vmin, vmax=vmax, axes=ax,
                         cmap=cmap[0], image_interp='bilinear', contours=0,
                         outlines=outlines, show=False, sphere=sphere)

    if colorbar:
        cbar, cax = _add_colorbar(ax, im, cmap, pad=0.25, title=None,
                                  size="10%", format=cbar_fmt)
        cbar.set_ticks((vmin, vmax))
        if unit is not None:
            cbar.ax.set_ylabel(unit, fontsize=8)
        cbar.ax.tick_params(labelsize=8)


@verbose
def plot_epochs_psd_topomap(epochs, bands=None, vmin=None, vmax=None,
                            tmin=None, tmax=None, proj=False,
                            bandwidth=None, adaptive=False, low_bias=True,
                            normalization='length', ch_type=None,
                            cmap=None, agg_fun=None, dB=False, n_jobs=1,
                            normalize=False, cbar_fmt='auto',
                            outlines='head', axes=None, show=True,
                            sphere=None, vlim=(None, None), verbose=None):
    """Plot the topomap of the power spectral density across epochs.

    Parameters
    ----------
    epochs : instance of Epochs
        The epochs object.
    %(psd_topo_bands)s
    vmin : None
        Deprecated; use ``vlim`` instead.
    vmax : None
        Deprecated; use ``vlim`` instead.
    tmin : float | None
        Start time to consider.
    tmax : float | None
        End time to consider.
    proj : bool
        Apply projection.
    bandwidth : float
        The bandwidth of the multi taper windowing function in Hz. The default
        value is a window half-bandwidth of 4 Hz.
    adaptive : bool
        Use adaptive weights to combine the tapered spectra into PSD
        (slow, use n_jobs >> 1 to speed up computation).
    low_bias : bool
        Only use tapers with more than 90%% spectral concentration within
        bandwidth.
    normalization : str
        Either "full" or "length" (default). If "full", the PSD will
        be normalized by the sampling rate as well as the length of
        the signal (as in nitime).
    ch_type : 'mag' | 'grad' | 'planar1' | 'planar2' | 'eeg' | None
        The channel type to plot. For 'grad', the gradiometers are collected in
        pairs and the mean for each pair is plotted. If None, then first
        available channel type from order given above is used. Defaults to
        None.
    %(psd_topo_cmap)s
    %(psd_topo_agg_fun)s
    %(psd_topo_dB)s
    %(n_jobs)s
    %(psd_topo_normalize)s
    %(psd_topo_cbar_fmt)s
    %(topomap_outlines)s
    %(psd_topo_axes)s
    show : bool
        Show figure if True.
    %(topomap_sphere_auto)s
    %(psd_topo_vlim_joint)s
    %(verbose)s

    Returns
    -------
    fig : instance of Figure
        Figure distributing one image per channel across sensor topography.
    """
    ch_type = _get_ch_type(epochs, ch_type)
    units = _handle_default('units', None)
    unit = units[ch_type]

    picks, pos, merge_channels, names, ch_type, sphere, clip_origin = \
        _prepare_topomap_plot(epochs, ch_type, sphere=sphere)
    outlines = _make_head_outlines(sphere, pos, outlines, clip_origin)

    psds, freqs = psd_multitaper(epochs, tmin=tmin, tmax=tmax,
                                 bandwidth=bandwidth, adaptive=adaptive,
                                 low_bias=low_bias,
                                 normalization=normalization, picks=picks,
                                 proj=proj, n_jobs=n_jobs)
    psds = np.mean(psds, axis=0)

    if merge_channels:
        psds, names = _merge_ch_data(psds, ch_type, names, method='mean')

    return plot_psds_topomap(
        psds=psds, freqs=freqs, pos=pos, agg_fun=agg_fun, vmin=vmin,
        vmax=vmax, bands=bands, cmap=cmap, dB=dB, normalize=normalize,
        cbar_fmt=cbar_fmt, outlines=outlines, axes=axes, show=show,
        sphere=sphere, vlim=vlim, unit=unit, ch_type=ch_type)


@fill_doc
def plot_psds_topomap(
        psds, freqs, pos, agg_fun=None, vmin=None, vmax=None, bands=None,
        cmap=None, dB=True, normalize=False, cbar_fmt='%0.3f', outlines='head',
        axes=None, show=True, sphere=None, vlim=(None, None), unit=None,
        ch_type='eeg'):
    """Plot spatial maps of PSDs.

    Parameters
    ----------
    psds : np.ndarray of float, shape (n_channels, n_freqs)
        Power spectral densities
    freqs : np.ndarray of float, shape (n_freqs)
        Frequencies used to compute psds.
    pos : numpy.ndarray of float, shape (n_sensors, 2)
        The positions of the sensors.
    %(psd_topo_agg_fun)s
    vmin : None
        Deprecated; use ``vlim`` instead.
    vmax : None
        Deprecated; use ``vlim`` instead.
    %(psd_topo_bands)s
    %(psd_topo_cmap)s
    %(psd_topo_dB)s
    %(psd_topo_normalize)s
    %(psd_topo_cbar_fmt)s
    %(topomap_outlines)s
    %(psd_topo_axes)s
    show : bool
        Show figure if True.
    %(topomap_sphere)s
    %(psd_topo_vlim_joint)s
    unit : str | None
        Measurement unit to be displayed with the colorbar. If ``None``, no
        unit is displayed (only "power" or "dB" as appropriate).
    %(topomap_ch_type)s

    Returns
    -------
    fig : instance of matplotlib.figure.Figure
        Figure with a topomap subplot for each band.
    """
    import matplotlib.pyplot as plt
    sphere = _check_sphere(sphere)

    if cbar_fmt == 'auto':
        cbar_fmt = '%0.1f' if dB else '%0.3f'

    if vmin is not None or vmax is not None:
        msg = ('"vmin" and "vmax" are deprecated and will be removed in '
               'version 0.22. Use "vlim" instead. ')
        if vlim == (None, None):
            msg += ('Since you didn\'t specify "vlim", your provided values '
                    'of "vmin" and "vmax" will be used.')
            vlim = (vmin, vmax)
        else:
            msg += ('Your provided values for "vlim" will be used, and "vmin" '
                    'and "vmax" will be ignored.')
        warn(msg, DeprecationWarning)

    if bands is None:
        bands = [(0, 4, 'Delta (0-4 Hz)'), (4, 8, 'Theta (4-8 Hz)'),
                 (8, 12, 'Alpha (8-12 Hz)'), (12, 30, 'Beta (12-30 Hz)'),
                 (30, 45, 'Gamma (30-45 Hz)')]
    else:  # upconvert single freqs to band upper/lower edges as needed
        bin_spacing = np.diff(freqs)[0]
        bin_edges = np.array([0, bin_spacing]) - bin_spacing / 2
        bands = [tuple(bin_edges + freqs[np.argmin(np.abs(freqs - band[0]))]) +
                 (band[1],) if len(band) == 2 else band for band in bands]

    if agg_fun is None:
        agg_fun = np.sum if normalize else np.mean

    if normalize:
        psds /= psds.sum(axis=-1, keepdims=True)
        assert np.allclose(psds.sum(axis=-1), 1.)

    n_axes = len(bands)
    if axes is not None:
        _validate_if_list_of_axes(axes, n_axes)
        fig = axes[0].figure
    else:
        fig, axes = plt.subplots(1, n_axes, figsize=(2 * n_axes, 1.5))
        if n_axes == 1:
            axes = [axes]

    # handle vmin/vmax
    if vlim == 'joint':
        _freq_masks = [(fmin < freqs) & (freqs < fmax)
                       for (fmin, fmax, _) in bands]
        _datas = [agg_fun(psds[:, _freq_mask], axis=1)
                  for _freq_mask in _freq_masks]
        _datas = [10 * np.log10(_d) if (dB and not normalize) else _d
                  for _d in _datas]
        vmin = np.array(_datas).min()
        vmax = np.array(_datas).max()
    else:
        vmin, vmax = vlim

    if unit is None:
        unit = 'dB' if dB and not normalize else 'power'
    else:
        if '/' in unit:
            unit = '(%s)' % unit
        unit += '²/Hz'
        if dB and not normalize:
            unit += ' (dB)'

    for ax, (fmin, fmax, title) in zip(axes, bands):
        freq_mask = (fmin < freqs) & (freqs < fmax)
        if freq_mask.sum() == 0:
            raise RuntimeError('No frequencies in band "%s" (%s, %s)'
                               % (title, fmin, fmax))
        data = agg_fun(psds[:, freq_mask], axis=1)
        if dB and not normalize:
            data = 10 * np.log10(data)

        _plot_topomap_multi_cbar(data, pos, ax, title=title, vmin=vmin,
                                 vmax=vmax, cmap=cmap, outlines=outlines,
                                 colorbar=True, unit=unit, cbar_fmt=cbar_fmt,
                                 sphere=sphere, ch_type=ch_type)
    tight_layout(fig=fig)
    fig.canvas.draw()
    plt_show(show)
    return fig


@fill_doc
def plot_layout(layout, picks=None, show=True):
    """Plot the sensor positions.

    Parameters
    ----------
    layout : None | Layout
        Layout instance specifying sensor positions.
    %(picks_nostr)s
    show : bool
        Show figure if True. Defaults to True.

    Returns
    -------
    fig : instance of Figure
        Figure containing the sensor topography.

    Notes
    -----
    .. versionadded:: 0.12.0
    """
    import matplotlib.pyplot as plt
    fig = plt.figure(figsize=(max(plt.rcParams['figure.figsize']),) * 2)
    ax = fig.add_subplot(111)
    fig.subplots_adjust(left=0, bottom=0, right=1, top=1, wspace=None,
                        hspace=None)
    ax.set(xticks=[], yticks=[], aspect='equal')
    pos = np.array([(p[0] + p[2] / 2., p[1] + p[3] / 2.) for p in layout.pos])
    outlines = dict(border=([0, 1, 1, 0, 0], [0, 0, 1, 1, 0]))
    _draw_outlines(ax, outlines)
    picks = _picks_to_idx(len(layout.names), picks)
    pos = pos[picks]
    names = np.array(layout.names)[picks]
    for ii, (this_pos, ch_id) in enumerate(zip(pos, names)):
        ax.annotate(ch_id, xy=this_pos[:2], horizontalalignment='center',
                    verticalalignment='center', size='x-small')
    ax.axis('off')
    tight_layout(fig=fig, pad=0, w_pad=0, h_pad=0)
    plt_show(show)
    return fig


def _onselect(eclick, erelease, tfr, pos, ch_type, itmin, itmax, ifmin, ifmax,
              cmap, fig, layout=None):
    """Handle drawing average tfr over channels called from topomap."""
    import matplotlib.pyplot as plt
    from matplotlib.collections import PathCollection
    ax = eclick.inaxes
    xmin = min(eclick.xdata, erelease.xdata)
    xmax = max(eclick.xdata, erelease.xdata)
    ymin = min(eclick.ydata, erelease.ydata)
    ymax = max(eclick.ydata, erelease.ydata)
    indices = ((pos[:, 0] < xmax) & (pos[:, 0] > xmin) &
               (pos[:, 1] < ymax) & (pos[:, 1] > ymin))
    colors = ['r' if ii else 'k' for ii in indices]
    indices = np.where(indices)[0]
    for collection in ax.collections:
        if isinstance(collection, PathCollection):  # this is our "scatter"
            collection.set_color(colors)
    ax.figure.canvas.draw()
    if len(indices) == 0:
        return
    data = tfr.data
    if ch_type == 'mag':
        picks = pick_types(tfr.info, meg=ch_type, ref_meg=False)
        data = np.mean(data[indices, ifmin:ifmax, itmin:itmax], axis=0)
        chs = [tfr.ch_names[picks[x]] for x in indices]
    elif ch_type == 'grad':
        grads = _pair_grad_sensors(tfr.info, layout=layout,
                                   topomap_coords=False)
        idxs = list()
        for idx in indices:
            idxs.append(grads[idx * 2])
            idxs.append(grads[idx * 2 + 1])  # pair of grads
        data = np.mean(data[idxs, ifmin:ifmax, itmin:itmax], axis=0)
        chs = [tfr.ch_names[x] for x in idxs]
    elif ch_type == 'eeg':
        picks = pick_types(tfr.info, meg=False, eeg=True, ref_meg=False)
        data = np.mean(data[indices, ifmin:ifmax, itmin:itmax], axis=0)
        chs = [tfr.ch_names[picks[x]] for x in indices]
    logger.info('Averaging TFR over channels ' + str(chs))
    if len(fig) == 0:
        fig.append(figure_nobar())
    if not plt.fignum_exists(fig[0].number):
        fig[0] = figure_nobar()
    ax = fig[0].add_subplot(111)
    itmax = len(tfr.times) - 1 if itmax is None else min(itmax,
                                                         len(tfr.times) - 1)
    ifmax = len(tfr.freqs) - 1 if ifmax is None else min(ifmax,
                                                         len(tfr.freqs) - 1)
    if itmin is None:
        itmin = 0
    if ifmin is None:
        ifmin = 0
    extent = (tfr.times[itmin] * 1e3, tfr.times[itmax] * 1e3, tfr.freqs[ifmin],
              tfr.freqs[ifmax])

    title = 'Average over %d %s channels.' % (len(chs), ch_type)
    ax.set_title(title)
    ax.set_xlabel('Time (ms)')
    ax.set_ylabel('Frequency (Hz)')
    img = ax.imshow(data, extent=extent, aspect="auto", origin="lower",
                    cmap=cmap)
    if len(fig[0].get_axes()) < 2:
        fig[0].get_axes()[1].cbar = fig[0].colorbar(mappable=img)
    else:
        fig[0].get_axes()[1].cbar.on_mappable_changed(mappable=img)
    fig[0].canvas.draw()
    plt.figure(fig[0].number)
    plt_show(True)


def _prepare_topomap(pos, ax, check_nonzero=True):
    """Prepare the topomap axis and check positions.

    Hides axis frame and check that position information is present.
    """
    _hide_frame(ax)
    if check_nonzero and not pos.any():
        raise RuntimeError('No position information found, cannot compute '
                           'geometries for topomap.')


def _hide_frame(ax):
    """Hide axis frame for topomaps."""
    ax.get_yticks()
    ax.xaxis.set_ticks([])
    ax.yaxis.set_ticks([])
    ax.set_frame_on(False)


def _init_anim(ax, ax_line, ax_cbar, params, merge_channels, sphere):
    """Initialize animated topomap."""
    from matplotlib import pyplot as plt, patches
    logger.info('Initializing animation...')
    data = params['data']
    items = list()
    if params['butterfly']:
        all_times = params['all_times']
        for idx in range(len(data)):
            ax_line.plot(all_times, data[idx], color='k', lw=1)
        vmin, vmax = _setup_vmin_vmax(data, None, None)
        ax_line.set(yticks=np.around(np.linspace(vmin, vmax, 5), -1),
                    xlim=all_times[[0, -1]])
        params['line'] = ax_line.axvline(all_times[0], color='r')
        items.append(params['line'])
    if merge_channels:
        from mne.channels.layout import _merge_ch_data
        data, _ = _merge_ch_data(data, 'grad', [])
    norm = True if np.min(data) > 0 else False
    cmap = 'Reds' if norm else 'RdBu_r'

    vmin, vmax = _setup_vmin_vmax(data, None, None, norm)

    outlines = _make_head_outlines(sphere, params['pos'], 'head',
                                   params['clip_origin'])

    _hide_frame(ax)
    extent, Xi, Yi, interp = _setup_interp(
        params['pos'], 64, 'box', sphere, outlines, 0)
    params['Zis'] = list()
    for frame in params['frames']:
        params['Zis'].append(interp.set_values(data[:, frame])(Xi, Yi))
    Zi = params['Zis'][0]
    zi_min = np.nanmin(params['Zis'])
    zi_max = np.nanmax(params['Zis'])
    cont_lims = np.linspace(zi_min, zi_max, 7, endpoint=False)[1:]
    params.update({'vmin': vmin, 'vmax': vmax, 'Xi': Xi, 'Yi': Yi, 'Zi': Zi,
                   'extent': extent, 'cmap': cmap, 'cont_lims': cont_lims})
    # plot map and contour
    im = ax.imshow(Zi, cmap=cmap, vmin=vmin, vmax=vmax, origin='lower',
                   aspect='equal', extent=extent,
                   interpolation='bilinear')
    ax.autoscale(enable=True, tight=True)
    plt.colorbar(im, cax=ax_cbar)
    cont = ax.contour(Xi, Yi, Zi, levels=cont_lims, colors='k', linewidths=1)

    patch_ = patches.Ellipse((0, 0),
                             2 * outlines['clip_radius'][0],
                             2 * outlines['clip_radius'][1],
                             clip_on=True,
                             transform=ax.transData)
    im.set_clip_path(patch_)
    text = ax.text(0.55, 0.95, '', transform=ax.transAxes, va='center',
                   ha='right')
    params['text'] = text
    items.append(im)
    items.append(text)
    for col in cont.collections:
        col.set_clip_path(patch_)

    outlines_ = _draw_outlines(ax, outlines)

    params.update({'patch': patch_, 'outlines': outlines_})
    ax.figure.tight_layout()
    return tuple(items) + tuple(cont.collections)


def _animate(frame, ax, ax_line, params):
    """Update animated topomap."""
    if params['pause']:
        frame = params['frame']
    time_idx = params['frames'][frame]

    if params['time_unit'] == 'ms':
        title = '%6.0f ms' % (params['times'][frame] * 1e3,)
    else:
        title = '%6.3f s' % (params['times'][frame],)
    if params['blit']:
        text = params['text']
    else:
        ax.cla()  # Clear old contours.
        text = ax.text(0.45, 1.15, '', transform=ax.transAxes)
        for k, (x, y) in params['outlines'].items():
            if 'mask' in k:
                continue
            ax.plot(x, y, color='k', linewidth=1, clip_on=False)

    _hide_frame(ax)
    text.set_text(title)

    vmin = params['vmin']
    vmax = params['vmax']
    Xi = params['Xi']
    Yi = params['Yi']
    Zi = params['Zis'][frame]
    extent = params['extent']
    cmap = params['cmap']
    patch = params['patch']

    im = ax.imshow(Zi, cmap=cmap, vmin=vmin, vmax=vmax, origin='lower',
                   aspect='equal', extent=extent, interpolation='bilinear')
    cont_lims = params['cont_lims']
    with warnings.catch_warnings(record=True):
        warnings.simplefilter('ignore')
        cont = ax.contour(
            Xi, Yi, Zi, levels=cont_lims, colors='k', linewidths=1)

    im.set_clip_path(patch)
    for col in cont.collections:
        col.set_clip_path(patch)

    items = [im, text]
    if params['butterfly']:
        all_times = params['all_times']
        line = params['line']
        line.remove()
        ylim = ax_line.get_ylim()
        params['line'] = ax_line.axvline(all_times[time_idx], color='r')
        ax_line.set_ylim(ylim)
        items.append(params['line'])
    params['frame'] = frame
    return tuple(items) + tuple(cont.collections)


def _pause_anim(event, params):
    """Pause or continue the animation on mouse click."""
    params['pause'] = not params['pause']


def _key_press(event, params):
    """Handle key presses for the animation."""
    if event.key == 'left':
        params['pause'] = True
        params['frame'] = max(params['frame'] - 1, 0)
    elif event.key == 'right':
        params['pause'] = True
        params['frame'] = min(params['frame'] + 1, len(params['frames']) - 1)


def _topomap_animation(evoked, ch_type, times, frame_rate, butterfly, blit,
                       show, time_unit, sphere):
    """Make animation of evoked data as topomap timeseries.

    See mne.evoked.Evoked.animate_topomap.
    """
    from matplotlib import pyplot as plt, animation
    if ch_type is None:
        ch_type = _picks_by_type(evoked.info)[0][0]
    if ch_type not in ('mag', 'grad', 'eeg',
                       'hbo', 'hbr', 'fnirs_od', 'fnirs_cw_amplitude'):
        raise ValueError("Channel type not supported. Supported channel "
                         "types include 'mag', 'grad', 'eeg'. 'hbo', 'hbr', "
                         "'fnirs_cw_amplitude', and 'fnirs_od'.")
    time_unit, _ = _check_time_unit(time_unit, evoked.times)
    if times is None:
        times = np.linspace(evoked.times[0], evoked.times[-1], 10)
    times = np.array(times)

    if times.ndim != 1:
        raise ValueError('times must be 1D, got %d dimensions' % times.ndim)
    if max(times) > evoked.times[-1] or min(times) < evoked.times[0]:
        raise ValueError('All times must be inside the evoked time series.')
    frames = [np.abs(evoked.times - time).argmin() for time in times]

    blit = False if plt.get_backend() == 'MacOSX' else blit
    picks, pos, merge_channels, _, ch_type, sphere, clip_origin = \
        _prepare_topomap_plot(evoked, ch_type, sphere=sphere)
    data = evoked.data[picks, :]
    data *= _handle_default('scalings')[ch_type]

    fig = plt.figure(figsize=(6, 5))
    shape = (8, 12)
    colspan = shape[1] - 1
    rowspan = shape[0] - bool(butterfly)
    ax = plt.subplot2grid(shape, (0, 0), rowspan=rowspan, colspan=colspan)
    if butterfly:
        ax_line = plt.subplot2grid(shape, (rowspan, 0), colspan=colspan)
    else:
        ax_line = None
    if isinstance(frames, Integral):
        frames = np.linspace(0, len(evoked.times) - 1, frames).astype(int)
    ax_cbar = plt.subplot2grid(shape, (0, colspan), rowspan=rowspan)
    ax_cbar.set_title(_handle_default('units')[ch_type], fontsize=10)

    params = dict(data=data, pos=pos, all_times=evoked.times, frame=0,
                  frames=frames, butterfly=butterfly, blit=blit,
                  pause=False, times=times, time_unit=time_unit,
                  clip_origin=clip_origin)
    init_func = partial(_init_anim, ax=ax, ax_cbar=ax_cbar, ax_line=ax_line,
                        params=params, merge_channels=merge_channels,
                        sphere=sphere)
    animate_func = partial(_animate, ax=ax, ax_line=ax_line, params=params)
    pause_func = partial(_pause_anim, params=params)
    fig.canvas.mpl_connect('button_press_event', pause_func)
    key_press_func = partial(_key_press, params=params)
    fig.canvas.mpl_connect('key_press_event', key_press_func)
    if frame_rate is None:
        frame_rate = evoked.info['sfreq'] / 10.
    interval = 1000 / frame_rate  # interval is in ms
    anim = animation.FuncAnimation(fig, animate_func, init_func=init_func,
                                   frames=len(frames), interval=interval,
                                   blit=blit)
    fig.mne_animation = anim  # to make sure anim is not garbage collected
    plt_show(show, block=False)
    if 'line' in params:
        # Finally remove the vertical line so it does not appear in saved fig.
        params['line'].remove()

    return fig, anim


def _set_contour_locator(vmin, vmax, contours):
    """Set correct contour levels."""
    locator = None
    if isinstance(contours, Integral) and contours > 0:
        from matplotlib import ticker
        # nbins = ticks - 1, since 2 of the ticks are vmin and vmax, the
        # correct number of bins is equal to contours + 1.
        locator = ticker.MaxNLocator(nbins=contours + 1)
        contours = locator.tick_values(vmin, vmax)
    return locator, contours


def _plot_corrmap(data, subjs, indices, ch_type, ica, label, show, outlines,
                  cmap, contours, template=False, sphere=None):
    """Customize ica.plot_components for corrmap."""
    if not template:
        title = 'Detected components'
        if label is not None:
            title += ' of type ' + label
    else:
        title = "Supplied template"

    picks = list(range(len(data)))

    p = 20
    if len(picks) > p:  # plot components by sets of 20
        n_components = len(picks)
        figs = [_plot_corrmap(data[k:k + p], subjs[k:k + p],
                              indices[k:k + p], ch_type, ica, label, show,
                              outlines=outlines, cmap=cmap, contours=contours)
                for k in range(0, n_components, p)]
        return figs
    elif np.isscalar(picks):
        picks = [picks]

    data_picks, pos, merge_channels, names, _, sphere, clip_origin = \
        _prepare_topomap_plot(ica, ch_type, sphere=sphere)
    outlines = _make_head_outlines(sphere, pos, outlines, clip_origin)

    data = np.atleast_2d(data)
    data = data[:, data_picks]

    # prepare data for iteration
    fig, axes, _, _ = _prepare_trellis(len(picks), ncols=5)
    fig.suptitle(title)

    for ii, data_, ax, subject, idx in zip(picks, data, axes, subjs, indices):
        if template:
            ttl = 'Subj. {}, {}'.format(subject, ica._ica_names[idx])
            ax.set_title(ttl, fontsize=12)
        else:
            ax.set_title('Subj. {}'.format(subject))
        if merge_channels:
            data_, _ = _merge_ch_data(data_, ch_type, [])
        vmin_, vmax_ = _setup_vmin_vmax(data_, None, None)
        plot_topomap(data_.flatten(), pos, vmin=vmin_, vmax=vmax_,
                     res=64, axes=ax, cmap=cmap, outlines=outlines,
                     contours=contours, show=False, image_interp='bilinear')[0]
        _hide_frame(ax)
    tight_layout(fig=fig)
    fig.subplots_adjust(top=0.8)
    fig.canvas.draw()
    plt_show(show)
    return fig


def _trigradient(x, y, z):
    """Take gradients of z on a mesh."""
    from matplotlib.tri import CubicTriInterpolator, Triangulation
    with warnings.catch_warnings():  # catch matplotlib warnings
        warnings.filterwarnings("ignore", category=DeprecationWarning)
        tri = Triangulation(x, y)
        tci = CubicTriInterpolator(tri, z)
        dx, dy = tci.gradient(tri.x, tri.y)
    return dx, dy


@fill_doc
def plot_arrowmap(data, info_from, info_to=None, scale=3e-10, vmin=None,
                  vmax=None, cmap=None, sensors=True, res=64, axes=None,
                  names=None, show_names=False, mask=None, mask_params=None,
                  outlines='head', contours=6, image_interp='bilinear',
                  show=True, onselect=None, extrapolate=_EXTRAPOLATE_DEFAULT,
                  sphere=None):
    """Plot arrow map.

    Compute arrowmaps, based upon the Hosaka-Cohen transformation
    :footcite:`CohenHosaka1976`, these arrows represents an estimation of the
    current flow underneath the MEG sensors. They are a poor man's MNE.

    Since planar gradiometers takes gradients along latitude and longitude,
    they need to be projected to the flattened manifold span by magnetometer
    or radial gradiometers before taking the gradients in the 2D Cartesian
    coordinate system for visualization on the 2D topoplot. You can use the
    ``info_from`` and ``info_to`` parameters to interpolate from
    gradiometer data to magnetometer data.

    Parameters
    ----------
    data : array, shape (n_channels,)
        The data values to plot.
    info_from : instance of Info
        The measurement info from data to interpolate from.
    info_to : instance of Info | None
        The measurement info to interpolate to. If None, it is assumed
        to be the same as info_from.
    scale : float, default 3e-10
        To scale the arrows.
    vmin : float | callable | None
        The value specifying the lower bound of the color range.
        If None, and vmax is None, -vmax is used. Else np.min(data).
        If callable, the output equals vmin(data). Defaults to None.
    vmax : float | callable | None
        The value specifying the upper bound of the color range.
        If None, the maximum absolute value is used. If callable, the output
        equals vmax(data). Defaults to None.
    cmap : matplotlib colormap | None
        Colormap to use. If None, 'Reds' is used for all positive data,
        otherwise defaults to 'RdBu_r'.
    sensors : bool | str
        Add markers for sensor locations to the plot. Accepts matplotlib plot
        format string (e.g., 'r+' for red plusses). If True (default), circles
        will be used.
    res : int
        The resolution of the topomap image (n pixels along each side).
    axes : instance of Axes | None
        The axes to plot to. If None, a new figure will be created.
    names : list | None
        List of channel names. If None, channel names are not plotted.
    %(topomap_show_names)s
        If ``True``, a list of names must be provided (see ``names`` keyword).
    mask : ndarray of bool, shape (n_channels, n_times) | None
        The channels to be marked as significant at a given time point.
        Indices set to ``True`` will be considered. Defaults to None.
    mask_params : dict | None
        Additional plotting parameters for plotting significant sensors.
        Default (None) equals::

            dict(marker='o', markerfacecolor='w', markeredgecolor='k',
                 linewidth=0, markersize=4)
    %(topomap_outlines)s
    contours : int | array of float
        The number of contour lines to draw. If 0, no contours will be drawn.
        If an array, the values represent the levels for the contours. The
        values are in µV for EEG, fT for magnetometers and fT/m for
        gradiometers. Defaults to 6.
    image_interp : str
        The image interpolation to be used. All matplotlib options are
        accepted.
    show : bool
        Show figure if True.
    onselect : callable | None
        Handle for a function that is called when the user selects a set of
        channels by rectangle selection (matplotlib ``RectangleSelector``). If
        None interactive selection is disabled. Defaults to None.
    %(topomap_extrapolate)s

        .. versionadded:: 0.18
    %(topomap_sphere_auto)s

    Returns
    -------
    fig : matplotlib.figure.Figure
        The Figure of the plot.

    Notes
    -----
    .. versionadded:: 0.17

    References
    ----------
    .. footbibliography::
    """
    from matplotlib import pyplot as plt
    from ..forward import _map_meg_or_eeg_channels

    sphere = _check_sphere(sphere, info_from)
    ch_type = _picks_by_type(info_from)

    if len(ch_type) > 1:
        raise ValueError('Multiple channel types are not supported.'
                         'All channels must either be of type \'grad\' '
                         'or \'mag\'.')
    else:
        ch_type = ch_type[0][0]

    if ch_type not in ('mag', 'grad'):
        raise ValueError("Channel type '%s' not supported. Supported channel "
                         "types are 'mag' and 'grad'." % ch_type)

    if info_to is None and ch_type == 'mag':
        info_to = info_from
    else:
        ch_type = _picks_by_type(info_to)
        if len(ch_type) > 1:
            raise ValueError("Multiple channel types are not supported.")
        else:
            ch_type = ch_type[0][0]

        if ch_type != 'mag':
            raise ValueError("only 'mag' channel type is supported. "
                             "Got %s" % ch_type)

    if info_to is not info_from:
        info_to = pick_info(info_to, pick_types(info_to, meg=True))
        info_from = pick_info(info_from, pick_types(info_from, meg=True))
        # XXX should probably support the "origin" argument
        mapping = _map_meg_or_eeg_channels(
            info_from, info_to, origin=(0., 0., 0.04), mode='accurate')
        data = np.dot(mapping, data)

    _, pos, _, _, _, sphere, clip_origin = \
        _prepare_topomap_plot(info_to, 'mag', sphere=sphere)
    outlines = _make_head_outlines(
        sphere, pos, outlines, clip_origin)
    if axes is None:
        fig, axes = plt.subplots()
    else:
        fig = axes.figure
    plot_topomap(data, pos, axes=axes, vmin=vmin, vmax=vmax, cmap=cmap,
                 sensors=sensors, res=res, names=names, show_names=show_names,
                 mask=mask, mask_params=mask_params, outlines=outlines,
                 contours=contours, image_interp=image_interp, show=False,
                 onselect=onselect, extrapolate=extrapolate, sphere=sphere,
                 ch_type=ch_type)
    x, y = tuple(pos.T)
    dx, dy = _trigradient(x, y, data)
    dxx = dy.data
    dyy = -dx.data
    axes.quiver(x, y, dxx, dyy, scale=scale, color='k', lw=1, clip_on=False)
    axes.figure.canvas.draw_idle()
    tight_layout(fig=fig)
    plt_show(show)

    return fig