Example of how one can use matplotlib transforms to inset an axes along each bar of a bar chart.

inset_axes_example.png

inset_histograms.py

from matplotlib.pyplot import subplots, show, rcParams
from numpy.random import default_rng
from pandas import DataFrame

rcParams['font.size'] = 16
for side in ['left', 'right', 'top', 'bottom']:
    rcParams[f'axes.spines.{side}'] = False

rng = default_rng(0)

df = DataFrame({
    '$\mu=40,\sigma=3$': rng.normal(40, 3, size=300),
    '$\mu=65,\sigma=5$': rng.normal(65, 5, size=300),
    '$\mu=50,\sigma=8$': rng.normal(50, 10, size=300),
})
agg_df = df.mean()

fig, ax = subplots(figsize=(8,8))
bars = ax.bar(agg_df.index, df.mean())

for rect, label in zip(bars, df.columns):
    x_data_pos = rect.get_x()

    hist_ax = ax.inset_axes(
        (x_data_pos, 0, rect.get_width(), 1),
        transform=ax.get_xaxis_transform(),
        sharey=ax
    )
    hist_ax.hist(
        df[label], orientation='horizontal',
        ec='gray', fc='white',
        alpha=.3, rwidth=.7
    )

    hist_ax.patch.set_alpha(0)
    hist_ax.xaxis.set_visible(False)
    hist_ax.yaxis.set_visible(False)

ax.patch.set_color('#f4f4f4')
ax.yaxis.grid(color='lightgray')
ax.yaxis.set_tick_params(width=0)
ax.set_axisbelow(True)

ax.set_title('Insetting a histogram on each bar\nof a bar chart')

show()

fig.savefig('inset_axes_example.png')