Matplotlib is a powerful Python library for creating visualizations. Legends are essential for clarity, and controlling their appearance, especially font size, is crucial for effective communication. This article explores multiple methods to adjust legend font sizes in your Matplotlib plots, empowering you to create visually appealing and easily understandable graphs.
Table of Contents
- Globally Adjusting Legend Font Size
- Controlling Legend Font Size Locally
- Fine-Grained Legend Customization
- Conclusion
- FAQ
Globally Adjusting Legend Font Size
This method modifies the font size for all legends within your script. It’s ideal for maintaining consistent font sizes across multiple plots. You achieve this by modifying the rcParams dictionary.
import matplotlib.pyplot as plt
import matplotlib as mpl
# Set the font size globally
mpl.rcParams['legend.fontsize'] = 12
# Sample plot
plt.plot([1, 2, 3], [4, 5, 6], label='Line 1')
plt.plot([1, 2, 3], [6, 4, 2], label='Line 2')
# Add legend
plt.legend()
plt.show()
This sets the legend font size to 12 points for all subsequent legends in your script. Remember, this change affects all legends globally.
Controlling Legend Font Size Locally
For more localized control, specify the font size directly within the plt.legend() function. This allows you to set different font sizes for individual legends.
import matplotlib.pyplot as plt
# Sample plot
plt.plot([1, 2, 3], [4, 5, 6], label='Line 1')
plt.plot([1, 2, 3], [6, 4, 2], label='Line 2')
# Add legend with specified font size
plt.legend(fontsize=14)
plt.show()
This sets the font size specifically for this legend to 14 points. This offers greater flexibility compared to the global rcParams method.
Fine-Grained Legend Customization
For precise control, directly access the legend object and modify its properties. This enables more complex customizations beyond just font size.
import matplotlib.pyplot as plt
# Sample plot
plt.plot([1, 2, 3], [4, 5, 6], label='Line 1')
plt.plot([1, 2, 3], [6, 4, 2], label='Line 2')
# Add legend
legend = plt.legend()
# Access legend text and set font size
for text in legend.get_texts():
text.set_fontsize(16)
plt.show()
This iterates through each legend entry and sets its font size individually. Useful for varying font sizes within a single legend.
Conclusion
This article presented three methods for adjusting Matplotlib legend font sizes: global settings (rcParams), local control (plt.legend(fontsize=...)), and fine-grained manipulation of legend objects. Select the method best suited to your needs and coding style.
FAQ
Q: Can I adjust other font properties besides size?
A: Yes, modify font family, style, weight, etc., using similar techniques. Explore the matplotlib.font_manager module for more details. For example, add fontweight='bold' to plt.legend() or use text.set_fontweight() in the third method.
Q: My legend overlaps the plot. How can I fix this?
A: Use the loc argument in plt.legend() to change the legend’s location, or manually position it with legend.set_bbox_to_anchor(). Consider adjusting plot size or reducing legend entries.
Q: My font size changes aren’t applied. What’s wrong?
A: Ensure plt.show() is called after setting the font size. Conflicts with font configurations or outdated Matplotlib installations might also cause problems. Try restarting your kernel or updating Matplotlib.