Matplotlib provides support for pie charts using the pie() function. This module allows the creation of various types of graphs, including pie charts, which visually represent data proportions in a circular format.

Creating a simple Pie Chart

Below is an example of how to create a basic pie chart using Matplotlib:

Example: Simple Pie Chart

import matplotlib.pyplot as plt

# Data to plot
labels = ['Angola', 'Brazil', 'Portugal', 'Cape Verde']
sizes = [1215, 2130, 2245, 2210]

# Define colors for each segment
colors = ['lightcoral', 'gold', 'yellowgreen', 'lightskyblue']

# Explode the first slice
explode = (0.1, 0, 0, 0)  

# Create pie chart
plt.pie(sizes, explode=explode, labels=labels, colors=colors, autopct='%1.1f%%', shadow=True, startangle=140)

# Ensure the pie chart is a circle
plt.axis('equal')

# Display the chart
plt.show()

Explanation of the Code:

  • The labels list defines the names of the categories.
  • The sizes list specifies the values corresponding to each category.
  • The colors list determines the color of each segment.
  • The explode parameter offsets a selected slice from the center.
  • The autopct='%1.1f%%' argument adds percentage labels to each segment.
  • The shadow=True argument adds a shadow effect.
  • The startangle=140 rotates the chart for better visibility.
  • The plt.axis('equal') ensures the pie chart remains circular.

Adding a Legend to the Pie Chart

You can add a legend to indicate what each segment represents using the legend() function.

Example: Pie Chart with Legend

import matplotlib.pyplot as plt

# Data to plot
labels = ['Angola', 'Brazil', 'Portugal', 'Cape Verde']
sizes = [1215, 2130, 2245, 2210]

# Define colors for each segment
colors = ['lightcoral', 'gold', 'yellowgreen', 'lightskyblue']

# Explode the first slice
explode = (0.1, 0, 0, 0)  

# Create pie chart
plt.pie(sizes, explode=explode, labels=labels, colors=colors, autopct='%1.1f%%', shadow=True, startangle=140)

# Add legend
plt.legend(labels, loc="upper right")

# Ensure the pie chart is a circle
plt.axis('equal')

# Display the chart
plt.show()

Legend positioning options

The loc parameter defines the position of the legend. Possible values include:

  • best (automatically selects the best position)
  • upper right
  • upper left
  • lower left
  • lower right
  • center left
  • center right
  • lower center
  • upper center
  • center

Conclusion

Pie charts are an effective way to visualize proportions in a dataset. Using Matplotlib, you can customize the chart by adjusting slice sizes, labels, colors, explosion effects, and legend positions.

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