How to set a single main title for all the subplots in Matplotlib?

How to Add a Main Title for All Subplots in Matplotlib

When creating multiple subplots using Matplotlib, it’s often helpful to include a single title that summarizes the entire figure. This can be done using the suptitle() method, which places a main title above all subplots.

Using suptitle() to Set a Figure-Wide Title

The suptitle() function belongs to the matplotlib.pyplot module. It allows you to define a main title for the whole figure, rather than individual subplot titles. Key parameters include:

• t: The main title text.
• x and y: Positioning coordinates (defaults center at top).
• fontsize: Size of the title text.
• fontweight: Weight of the font like 'bold' or 'light'.
• ha and va: Horizontal and vertical alignment.

Example: Simple Main Title on 2x2 Subplots

import matplotlib.pyplot as plt
import numpy as np

fig, ax = plt.subplots(2, 2)

for i in range(2):
    for j in range(2):
        ax[i, j].plot(np.random.rand(10))

fig.suptitle('Main Title Across All Subplots', fontsize=16)

plt.tight_layout()
plt.show()

This example plots four subplots in a 2x2 grid and places a single, centered title above them using suptitle().

Improving Layout with tight_layout()

Adding a figure-wide title can sometimes cause overlap with subplot elements. To resolve this, use tight_layout() along with the rect parameter:

plt.tight_layout(rect=[0, 0, 1, 0.95])

This adjusts the layout to leave some space at the top for the title.

Customizing the Title Appearance

fig.suptitle('Stylized Main Title', fontsize=20, fontweight='bold', ha='center')

You can easily adjust font size, weight, and alignment to style the main title as needed.

Conclusion

The suptitle() function is a simple and effective way to set a central title for all subplots in Matplotlib. Combined with layout adjustments like tight_layout(), it ensures your plots are both informative and visually well-organized.