Min/max markers on box plot are not visible with 'dark_background' theme

[sandyscott]

Min/max markers on box plot are not visible with 'dark_background' theme

The min & max markers (the short lines at the ends of the whiskers) aren't visible with the 'dark_background' theme

Code for reproduction

import pandas as pd
import matplotlib.pyplot as plt

# Data is from the pandas plotting demo
# https://pandas.pydata.org/docs/getting_started/intro_tutorials/04_plotting.html
air_quality = pd.read_csv("air_quality_no2.csv", index_col=0, parse_dates=True)

plt.style.use('default')
air_quality.plot.box()

plt.style.use('dark_background')
air_quality.plot.box()

Actual outcome

Software versions

• Matplotlib version: 3.3.1
• Matplotlib backend: module://ipykernel.pylab.backend_inline
• Python version: 3.8.6
• Jupyterlab version: 3.0.12
• Pandas: 1.2.3
• Operating system: Sage Math 9.2 installation running on Ubuntu 20.10 on WSL in windows 10 64-bit

[diegopetrola]

I tried to reproduce this somehow using only matplotlib and numpy and was unable to.
Here is an exemple code:

#Code taken from matplotlib.org/stable/gallery/index.html#
import numpy as np
import matplotlib.pyplot as plt
import pandas as pd

plt.style.use('dark_background')
# Fixing random state for reproducibility
np.random.seed(19680801)

# fake up some data
spread = np.random.rand(50) * 100
center = np.ones(25) * 50
flier_high = np.random.rand(10) * 100 + 100
flier_low = np.random.rand(10) * -100
data = np.concatenate((spread, center, flier_high, flier_low))

fig1, ax1 = plt.subplots()
ax1.set_title('Basic Plot')
ax1.boxplot(data)

And the outcome is:

I also briefly investigated pandas and it seems they have a function called _get_standard_colors() in line 83 of the script called boxplot.py. I am fairly confident that it is this function that overrides the theme and causes the issue.

If you manage to reproduce this without using pandas, please let us know but, as of now, I believe the issue should be redirected to them.

For now you can change the last line of your code to air_quality.plot.box(capprops=dict(color='white')) or any other color you like to have the markers appear in the figure. If you want further information on how to customize the colors of a boxplot you can read more here.

[jklymak]

Thanks @diegopetrola, I'll close this.

[sandyscott]

Thank you, I've reported the issue in pandas.