Composing Custom Legends#

Composing custom legends piece-by-piece.

Note

For more information on creating and customizing legends, see the following pages:

Sometimes you don't want a legend that is explicitly tied to data that you have plotted. For example, say you have plotted 10 lines, but don't want a legend item to show up for each one. If you simply plot the lines and call ax.legend(), you will get the following:

import matplotlib as mpl
from matplotlib import cycler
import matplotlib.pyplot as plt
import numpy as np

# Fixing random state for reproducibility
np.random.seed(19680801)

N = 10
data = (np.geomspace(1, 10, 100) + np.random.randn(N, 100)).T
cmap = plt.cm.coolwarm
mpl.rcParams['axes.prop_cycle'] = cycler(color=cmap(np.linspace(0, 1, N)))

fig, ax = plt.subplots()
lines = ax.plot(data)
ax.legend()
custom legends
No artists with labels found to put in legend.  Note that artists whose label start with an underscore are ignored when legend() is called with no argument.

Note that no legend entries were created. In this case, we can compose a legend using Matplotlib objects that aren't explicitly tied to the data that was plotted. For example:

from matplotlib.lines import Line2D
custom_lines = [Line2D([0], [0], color=cmap(0.), lw=4),
                Line2D([0], [0], color=cmap(.5), lw=4),
                Line2D([0], [0], color=cmap(1.), lw=4)]

fig, ax = plt.subplots()
lines = ax.plot(data)
ax.legend(custom_lines, ['Cold', 'Medium', 'Hot'])
custom legends

There are many other Matplotlib objects that can be used in this way. In the code below we've listed a few common ones.

from matplotlib.patches import Patch
from matplotlib.lines import Line2D

legend_elements = [Line2D([0], [0], color='b', lw=4, label='Line'),
                   Line2D([0], [0], marker='o', color='w', label='Scatter',
                          markerfacecolor='g', markersize=15),
                   Patch(facecolor='orange', edgecolor='r',
                         label='Color Patch')]

# Create the figure
fig, ax = plt.subplots()
ax.legend(handles=legend_elements, loc='center')

plt.show()
custom legends

Total running time of the script: ( 0 minutes 2.350 seconds)

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