Matplotlib 散点图图例创作之谜

Question

我有以下代码片段（c、s、x、y 的值是模型，但真实列表遵循相同的格式，只是更大。只使用了两种颜色 - 红色和绿色。所有列表大小相同）

问题是颜色图例未能实现。我完全不知道为什么。图例生成的代码片段基本上是来自文档的剪切粘贴，即 (https://matplotlib.org/3.1.1/gallery/lines_bars_and_markers/scatter_with_legend.html#sphx-glr-gallery-lines-bars-and-markers-scatter-with-legend-py)

有人知道吗？？

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
%matplotlib inline

c = [ 'g', 'r', 'r', 'g', 'g', 'r', 'r', 'r', 'g', 'r']
s = [ 10, 20, 10, 40, 60, 90, 90, 50, 60, 40]
x = [ 2.4, 3.0, 3.5, 3.5, 3.5, 3.5, 3.5, 2.4, 3.5, 3.5]
y = [24.0, 26.0, 20.0, 19.0, 19.0, 21.0, 20.0, 23.0, 20.0, 20.0]

fig, ax = plt.subplots()

scatter = plt.scatter(x, y, s=s, c=c, alpha=0.5)

# produce a legend with the unique colors from the scatter
handles, lables = scatter.legend_elements()
legend1 = ax.legend(handles, labels, loc="lower left", title="Colors")
ax.add_artist(legend1)

# produce a legend with a cross section of sizes from the scatter
handles, labels = scatter.legend_elements(prop="sizes", alpha=0.5)
legend2 = ax.legend(handles, labels, loc="upper right", ncol=2, title="Sizes")

plt.show()

绘图输出：

Answer 1

似乎 legend_elements() 仅在向 c= 传递要映射到颜色图的数字数组时使用。您可以通过在代码中将 c=c 替换为 c=s 进行测试，您将获得所需的输出。

就个人而言，我希望您的代码能够正常工作，也许值得在 matplotlib's github. EDIT: actually, there is already a discussion about this very issue on the issue tracker

将其作为错误或功能请求提出来

规避此限制的一种方法是用数字数组替换颜色名称数组，并创建一个自定义颜色图，将数组中的每个值映射到所需的颜色：

#c = [ 'g', 'r', 'r', 'g', 'g', 'r', 'r', 'r', 'g', 'r']
c = [0, 1, 1, 0, 0, 1, 1, 1, 0, 1]
cmap = matplotlib.colors.ListedColormap(['g','r'])
s = [ 10, 20, 10, 40, 60, 90, 90, 50, 60, 40]
x = [ 2.4, 3.0, 3.5, 3.5, 3.5, 3.5, 3.5, 2.4, 3.5, 3.5]
y = [24.0, 26.0, 20.0, 19.0, 19.0, 21.0, 20.0, 23.0, 20.0, 20.0]

fig, ax = plt.subplots()

scatter = plt.scatter(x, y, s=s, c=c, alpha=0.5, cmap=cmap)

# produce a legend with the unique colors from the scatter
handles, labels = scatter.legend_elements()
legend1 = ax.legend(handles, labels, loc="lower left", title="Colors")
ax.add_artist(legend1)

# produce a legend with a cross section of sizes from the scatter
handles, labels = scatter.legend_elements(prop="sizes", alpha=0.5)
legend2 = ax.legend(handles, labels, loc="upper right", ncol=2, title="Sizes")

plt.show()

Matplotlib 散点图图例创作之谜

Matplotlib Scatter Plot Legend Creation Mystery

python

matplotlib

colors

legend

legend-properties