How to Create and Annotate a Grouped Bar Chart Using Matplotlib in Python?

How to Plot and Annotate a Grouped Bar Chart

Plotting a grouped bar chart with Python's Matplotlib requires careful consideration of data manipulation, bar spacing, and labeling. Here's how to address your specific issue:

Data Preparation

• Instead of dividing each column by 2233 separately, use the div() method on the entire df to achieve the same effect in a single line: df = df.div(2233).

Pre-matplotlib 3.4.2

• Adjust the w value to 0.8 / 3 to correctly space the bars.

Post-matplotlib 3.4.2

• Utilize matplotlib.pyplot.bar_label and pandas.DataFrame.plot for a simpler and more elegant approach.

Annotation

• To label the bars, use the annotate() function within a loop that iterates over the patches.
• Adjust the positioning of the annotations based on the desired alignment and aesthetics.

Sample Code

<code class="python">import pandas as pd
import matplotlib.pyplot as plt

df = pd.DataFrame(...).div(2233)

ax = df.plot(kind='bar', color=colors, figsize=(20, 8), ylabel='Percentage', title="...")

for p in ax.patches:
    ax.annotate(f'{p.get_height():0.2f}', (p.get_x() + p.get_width() / 2., p.get_height()), ha='center', va='center', xytext=(0, 10), textcoords='offset points')</code>

This code will generate a grouped bar chart with annotated bar heights.

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