change specific subplot background color (outside of pie chart)

Question

I have the following subplots with pie charts, output by the code below.

I want to shade in a different color the background of the odd-numbered subplots (only the middle one in the image above), but I haven't been able make it work.

I looked at a few places and from a few answers to this question I tried both ax.set_facecolor('red') and ax.patch.set_facecolor('red'), none of which resulted in the alternative shading/coloring pattern I'm looking for.

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt

n = 3

nums_df = pd.DataFrame([np.random.randint(1, 20, size=5) for _ in xrange(n)])

row_labels = ["row {:d}".format(i) for i in xrange(n)]

nums_df.index = row_labels

# create a figure with n subplots
fig, axes = plt.subplots(1, n)

# create pie charts
for i, ax in enumerate(axes):
    ax.pie(nums_df.loc[row_labels[i]], labels=nums_df.loc[row_labels[i]])
    ax.axis("equal")
    if i%2 == 1:
        ax.set_facecolor('red')
        # ax.patch.set_facecolor('red')


plt.show()

ImportanceOfBeingErnest · Accepted Answer · 2018-02-26T19:20:43.690

By default the complete axes of a pie plot is "off". You can set it on, use the frame argument.

ax.pie(..., frame=True)

This produces ticks and ticklabels on the axes, hence, it might be better to set it on externally,

ax.pie(..., frame=False)
ax.set_frame_on(True)

In addition you probably want to set the spines off,

for _, spine in ax.spines.items():
    spine.set_visible(False)

or, in a single line

plt.setp(ax.spines.values(),visible=False)

Finally, for the ticklabels not to exceed the axes area, one may fix the axis range, e.g. ax.axis([-1,1,-1,1]) and use a smaller pie radius, e.g. radius=.27.

Complete code for reproduction

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt

n = 3
nums_df = pd.DataFrame([np.random.randint(1, 20, size=5) for _ in xrange(n)])
row_labels = ["row {:d}".format(i) for i in xrange(n)]
nums_df.index = row_labels

fig, axes = plt.subplots(1, n)

for i, ax in enumerate(axes):
    ax.pie(nums_df.loc[row_labels[i]], labels=nums_df.loc[row_labels[i]], frame=False, radius=0.27)
    ax.set_frame_on(True)
    ax.axis("equal")
    ax.axis([-1,1,-1,1])
    plt.setp(ax.spines.values(),visible=False)
    if i%2 == 1:
        ax.set_facecolor('red')

plt.show()

thank you! maybe this should be a separate question or an edit, but is there a simple way to extend that frame to cover the pie chart labels? Tried passing `gridspec_kw = {'width_ratios':[1,1.5,1]}` to `plt.subplots()` but that also makes middle pie chart larger, which isn't what I want. (I know I could put the numbers inside the pie chart but that doesn't work as well for small wedges.) — arturomp, Feb 26 '18 at 19:12
No the logic would be to make the pie chart smaller and fix the axis range, such that it sits inside the axes. I updated the answer. — ImportanceOfBeingErnest, Feb 26 '18 at 19:21

change specific subplot background color (outside of pie chart)

1 Answers1