BUG: stacked bar graphs show invalid label position due to invalid rectangle bottom when data is 0

[KinzigFlyer]

BUG: stacked bar graphs show invalid label position due to invalid rectangle bottom when data is 0

[KinzigFlyer]

Thanks @KevsterAmp for looking into this

[KinzigFlyer]

I don't think so,
Matplotlib does not provide stacking on it's own. You create a stacked bar by providing "bottom" parameter to the bars.
So I think bottom is calculated inside Pandas.
see this page in the official matplotlib documentation:
Stacked Bar charts

[KinzigFlyer]

I took the official programm, changed one of the Above values to 0 and added the bar-label. Works correctly.

import matplotlib.pyplot as plt
import numpy as np

# data from https://allisonhorst.github.io/palmerpenguins/

species = (
    "Adelie\n $\\mu=$3700.66g",
    "Chinstrap\n $\\mu=$3733.09g",
    "Gentoo\n $\\mu=5076.02g$",
)
weight_counts = {
    "Below": np.array([70, 31, 58]),
    "Above": np.array([82, 0, 66]),
}
width = 0.5

fig, ax = plt.subplots()
bottom = np.zeros(3)

for boolean, weight_count in weight_counts.items():
    p = ax.bar(species, weight_count, width, label=boolean, bottom=bottom)
    bottom += weight_count

ax.bar_label(p, weight_counts['Above'])
ax.set_title("Number of penguins with above average body mass")
ax.legend(loc="upper right")

plt.show()

[KinzigFlyer]

Converting the official example to a Pandas driven version shows the error:

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

# data from https://allisonhorst.github.io/palmerpenguins/
penguins = pd.DataFrame.from_dict([
    {'species': "Adelie", 'Below': 70.0, 'Above': 82.0},
    {'species': "Chinstrap", 'Below': 31.0, 'Above': 0.0},
    {'species': "Gentoo", 'Below': 58.0, 'Above': 66.0},
]).set_index('species')
width = 0.5

ax2 = penguins.plot.bar(stacked = True)

ax2.bar_label(ax2.containers[-1], penguins['Above'])
ax2.set_title("Number of penguins with above average body mass")
ax2.legend(loc="upper right")

plt.show()

[KevsterAmp]

take

[KevsterAmp]

All good, just waiting for this issue to be triaged by a maintainer before working on it.

[KevsterAmp]

@KinzigFlyer - seems like this is a problem on matplotlib not on the pandas itself

[KevsterAmp]

Good point, thank you

[rhshadrach]

Thanks for the report - PRs to fix are welcome!