Hatch-filled histograms

Hatching capabilities for plotting histograms.

import itertools
from collections import OrderedDict
from functools import partial

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.ticker as mticker
from cycler import cycler


def filled_hist(ax, edges, values, bottoms=None, orientation='v',
                **kwargs):
    """
    Draw a histogram as a stepped patch.

    Extra kwargs are passed through to `fill_between`

    Parameters
    ----------
    ax : Axes
        The axes to plot to

    edges : array
        A length n+1 array giving the left edges of each bin and the
        right edge of the last bin.

    values : array
        A length n array of bin counts or values

    bottoms : float or array, optional
        A length n array of the bottom of the bars.  If None, zero is used.

    orientation : {'v', 'h'}
       Orientation of the histogram.  'v' (default) has
       the bars increasing in the positive y-direction.

    Returns
    -------
    ret : PolyCollection
        Artist added to the Axes
    """
    print(orientation)
    if orientation not in 'hv':
        raise ValueError("orientation must be in {{'h', 'v'}} "
                         "not {o}".format(o=orientation))

    kwargs.setdefault('step', 'post')
    edges = np.asarray(edges)
    values = np.asarray(values)
    if len(edges) - 1 != len(values):
        raise ValueError('Must provide one more bin edge than value not: '
                         'len(edges): {lb} len(values): {lv}'.format(
                             lb=len(edges), lv=len(values)))

    if bottoms is None:
        bottoms = 0
    bottoms = np.broadcast_to(bottoms, values.shape)

    values = np.append(values, values[-1])
    bottoms = np.append(bottoms, bottoms[-1])
    if orientation == 'h':
        return ax.fill_betweenx(edges, values, bottoms,
                                **kwargs)
    elif orientation == 'v':
        return ax.fill_between(edges, values, bottoms,
                               **kwargs)
    else:
        raise AssertionError("you should never be here")


def stack_hist(ax, stacked_data, sty_cycle, bottoms=None,
               hist_func=None, labels=None,
               plot_func=None, plot_kwargs=None):
    """
    Parameters
    ----------
    ax : axes.Axes
        The axes to add artists too

    stacked_data : array or Mapping
        A (N, M) shaped array.  The first dimension will be iterated over to
        compute histograms row-wise

    sty_cycle : Cycler or operable of dict
        Style to apply to each set

    bottoms : array, default: 0
        The initial positions of the bottoms.

    hist_func : callable, optional
        Must have signature `bin_vals, bin_edges = f(data)`.
        `bin_edges` expected to be one longer than `bin_vals`

    labels : list of str, optional
        The label for each set.

        If not given and stacked data is an array defaults to 'default set {n}'

        If stacked_data is a mapping, and labels is None, default to the keys
        (which may come out in a random order).

        If stacked_data is a mapping and labels is given then only
        the columns listed by be plotted.

    plot_func : callable, optional
        Function to call to draw the histogram must have signature:

          ret = plot_func(ax, edges, top, bottoms=bottoms,
                          label=label, **kwargs)

    plot_kwargs : dict, optional
        Any extra kwargs to pass through to the plotting function.  This
        will be the same for all calls to the plotting function and will
        over-ride the values in cycle.

    Returns
    -------
    arts : dict
        Dictionary of artists keyed on their labels
    """
    # deal with default binning function
    if hist_func is None:
        hist_func = np.histogram

    # deal with default plotting function
    if plot_func is None:
        plot_func = filled_hist

    # deal with default
    if plot_kwargs is None:
        plot_kwargs = {}
    print(plot_kwargs)
    try:
        l_keys = stacked_data.keys()
        label_data = True
        if labels is None:
            labels = l_keys

    except AttributeError:
        label_data = False
        if labels is None:
            labels = itertools.repeat(None)

    if label_data:
        loop_iter = enumerate((stacked_data[lab], lab, s)
                              for lab, s in zip(labels, sty_cycle))
    else:
        loop_iter = enumerate(zip(stacked_data, labels, sty_cycle))

    arts = {}
    for j, (data, label, sty) in loop_iter:
        if label is None:
            label = 'dflt set {n}'.format(n=j)
        label = sty.pop('label', label)
        vals, edges = hist_func(data)
        if bottoms is None:
            bottoms = np.zeros_like(vals)
        top = bottoms + vals
        print(sty)
        sty.update(plot_kwargs)
        print(sty)
        ret = plot_func(ax, edges, top, bottoms=bottoms,
                        label=label, **sty)
        bottoms = top
        arts[label] = ret
    ax.legend(fontsize=10)
    return arts


# set up histogram function to fixed bins
edges = np.linspace(-3, 3, 20, endpoint=True)
hist_func = partial(np.histogram, bins=edges)

# set up style cycles
color_cycle = cycler(facecolor=plt.rcParams['axes.prop_cycle'][:4])
label_cycle = cycler(label=['set {n}'.format(n=n) for n in range(4)])
hatch_cycle = cycler(hatch=['/', '*', '+', '|'])

# Fixing random state for reproducibility
np.random.seed(19680801)

stack_data = np.random.randn(4, 12250)
dict_data = OrderedDict(zip((c['label'] for c in label_cycle), stack_data))

Work with plain arrays

fig, (ax1, ax2) = plt.subplots(1, 2, figsize=(9, 4.5), tight_layout=True)
arts = stack_hist(ax1, stack_data, color_cycle + label_cycle + hatch_cycle,
                  hist_func=hist_func)

arts = stack_hist(ax2, stack_data, color_cycle,
                  hist_func=hist_func,
                  plot_kwargs=dict(edgecolor='w', orientation='h'))
ax1.set_ylabel('counts')
ax1.set_xlabel('x')
ax2.set_xlabel('counts')
ax2.set_ylabel('x')

Out:

{}
{'facecolor': '#1f77b4', 'hatch': '/'}
{'facecolor': '#1f77b4', 'hatch': '/'}
v
{'facecolor': '#ff7f0e', 'hatch': '*'}
{'facecolor': '#ff7f0e', 'hatch': '*'}
v
{'facecolor': '#2ca02c', 'hatch': '+'}
{'facecolor': '#2ca02c', 'hatch': '+'}
v
{'facecolor': '#d62728', 'hatch': '|'}
{'facecolor': '#d62728', 'hatch': '|'}
v
{'edgecolor': 'w', 'orientation': 'h'}
{'facecolor': '#1f77b4'}
{'facecolor': '#1f77b4', 'edgecolor': 'w', 'orientation': 'h'}
h
{'facecolor': '#ff7f0e'}
{'facecolor': '#ff7f0e', 'edgecolor': 'w', 'orientation': 'h'}
h
{'facecolor': '#2ca02c'}
{'facecolor': '#2ca02c', 'edgecolor': 'w', 'orientation': 'h'}
h
{'facecolor': '#d62728'}
{'facecolor': '#d62728', 'edgecolor': 'w', 'orientation': 'h'}
h

Text(478.99999999999994, 0.5, 'x')

Work with labeled data

fig, (ax1, ax2) = plt.subplots(1, 2, figsize=(9, 4.5),
                               tight_layout=True, sharey=True)

arts = stack_hist(ax1, dict_data, color_cycle + hatch_cycle,
                  hist_func=hist_func)

arts = stack_hist(ax2, dict_data, color_cycle + hatch_cycle,
                  hist_func=hist_func, labels=['set 0', 'set 3'])
ax1.xaxis.set_major_locator(mticker.MaxNLocator(5))
ax1.set_xlabel('counts')
ax1.set_ylabel('x')
ax2.set_ylabel('x')

plt.show()

Out:

{}
{'facecolor': '#1f77b4', 'hatch': '/'}
{'facecolor': '#1f77b4', 'hatch': '/'}
v
{'facecolor': '#ff7f0e', 'hatch': '*'}
{'facecolor': '#ff7f0e', 'hatch': '*'}
v
{'facecolor': '#2ca02c', 'hatch': '+'}
{'facecolor': '#2ca02c', 'hatch': '+'}
v
{'facecolor': '#d62728', 'hatch': '|'}
{'facecolor': '#d62728', 'hatch': '|'}
v
{}
{'facecolor': '#1f77b4', 'hatch': '/'}
{'facecolor': '#1f77b4', 'hatch': '/'}
v
{'facecolor': '#ff7f0e', 'hatch': '*'}
{'facecolor': '#ff7f0e', 'hatch': '*'}
v

---

References

The use of the following functions, methods, classes and modules is shown in this example:

import matplotlib
matplotlib.axes.Axes.fill_betweenx
matplotlib.axes.Axes.fill_between
matplotlib.axis.Axis.set_major_locator

Out:

<function Axis.set_major_locator at 0x7f73be94d160>