How to add edge color to a histogram

• As part of the update to matplotlib 2.0 the edges on bar plots are turned off by default. However, this behavior can be globally changed with rcParams.
  • plt.rcParams["patch.force_edgecolor"] = True
• Alternatively, set the edgecolor / ec parameter in the plot call, and potentially increase the linewidth / lw parameter.
• Tested in python 3.11.4, pandas 2.0.3, matplotlib 3.7.1, seaborn 0.12.2

Imports and Sample Data

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

np.random.seed(2023)  # ensures the data is repeatable
x = np.random.randn(100)
df = pd.DataFrame(data=x, columns=['values'])

# precalculate the histogram values to plot a bar plot
counts, bins = np.histogram(x)

pandas

• Uses matplotlib as the default plotting backend.

ax = df.plot(kind='hist', ec="k")

matplotlib

.hist

plt.hist(x, ec="k")

.bar

fig, ax = plt.subplots()
ax.bar(x=range(len(counts)), height=counts, width=1, ec="k")

# sets the bin values at the bar edges
_ = ax.set_xticks(ticks=np.arange(0, len(bins)) - 0.5, labels=bins.round(2))

seaborn

• Is a high-level API for matplotlib.
• Figure-level vs. axes-level functions
• ec="k" is the default setting. However, ec can be used to set a different color or None.

.histplot

• An axes-level function.

ax = sns.histplot(data=df, x='values')

.displot

• A figure-level function.

g = sns.displot(data=df, kind='hist', x='values')

.distplot

• Replaced by histplot and displot.
• Set the edgecolor when creating a distplot, using the hist_kws argument.

ax = sns.distplot(x, hist_kws=dict(edgecolor="k", linewidth=2))

Example Plot