Скачать или смотреть Creating a Matplotlib Legend in a Separate Figure with PolyCollection Objects

Learn how to handle `PolyCollection` objects in `Matplotlib` to create a legend in a separate figure without errors.
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Creating a Matplotlib Legend in a Separate Figure with PolyCollection Objects

When using Matplotlib to create plots, sometimes you may encounter the need to have a separate figure for your legend. This can be particularly important when your plot contains different types of visual elements, such as lines and filled areas, which may behave differently when it comes to generating legends.

In this guide, we're going to address a common issue: how to include a PolyCollection object, which is typically created by the fill_between method, in a separate legend figure alongside Line2D objects. Let's dive into the problem and the solution!

The Problem

You have a plot that includes:

Two line plots created with regular plot functions.

An area filled between the two line plots using fill_between.

The challenge arises when you attempt to use the fill element in the legend of a separate figure, which results in an error:

[[See Video to Reveal this Text or Code Snippet]]

This error occurs because Matplotlib doesn't allow you to reuse elements from one figure in another. However, there is a workaround!

The Solution

To successfully create a legend that includes both line plots and the filled area, you will need to create new instances of Line2D and PolyCollection objects, copying the properties from the original elements. Here’s how you can do it step-by-step:

Step 1: Set Up Your Initial Plot

First, create your plot with the necessary line and fill elements:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Create a New Figure for the Legend

After you have created your main plot, create a new figure specifically for the legend:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Create New Legend Handles

Now you need to create new handle objects for the legend that replicate the properties of your original line and fill elements:

[[See Video to Reveal this Text or Code Snippet]]

Step 4: Add the New Handles to the Legend

Finally, add these new handles to the legend of your separate figure:

[[See Video to Reveal this Text or Code Snippet]]

Step 5: Display and Save Your Figures

Now that you have two figures—one for the plot and one for the legend—you can display or save them separately:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

Creating a separate legend figure in Matplotlib is a useful feature for improving your data visualizations. With the method outlined above, you can include different types of plot elements, such as PolyCollection objects, without running into errors.

Always remember: when dealing with Matplotlib, not all objects can be shared across figures, but with a little creativity, you can replicate their properties to customize legends to your liking.

Feel free to experiment with different styles and configurations to make your graphics stand out!