带有图例的 matplotlib 散点图 [英] matplotlib scatterplot with legend

问题描述

我有兴趣在散点图中绘制图例.我当前的代码看起来像这样

x=[1,2,3,4]y=[5,6,7,8]类 = [2,4,4,2]plt.scatter(x, y, c=classes, label=classes)plt.legend()

问题在于，在创建绘图时，图例显示为数组，而不是显示唯一标签及其类别.

我知道这是之前在诸如这个

如果类是字符串标签，解决方案看起来会略有不同，因为您需要从它们的索引中获取颜色，而不是使用类本身.

将 numpy 导入为 np导入 matplotlib.pyplot 作为 pltx=[1,2,3,4]y=[5,6,7,8]类 = ['X','Y','Z','X']unique = np.unique(classes)颜色 = [plt.cm.jet(i/float(len(unique)-1)) for i in range(len(unique))]对于 i, u 在 enumerate(unique) 中:xi = [x[j] for j in range(len(x)) if classes[j] == u]yi = [y[j] for j in range(len(x)) if classes[j] == u]plt.scatter(xi, yi, c=colors[i], label=str(u))plt.legend()plt.show()

I am interested in plotting a legend in my scatterplot. My current code looks like this

x=[1,2,3,4]
y=[5,6,7,8]
classes = [2,4,4,2]
plt.scatter(x, y, c=classes, label=classes)
plt.legend()

The problem is that when the plot is created, the legend is shown as an array instead of showing the unique labels and their classes.

I am aware this is a question discussed previously in threads such as this one, however I feel that my problem is even simpler and the solution there does not fits it. Also, in that example the person is specifying the colors however in my case I do know beforehand how many colors I'll need. Moreover, in this example the user is creating multiple scatters, each one with a unique color. Again, this is not what I want. My goal is to simply create the plot using an x,y array and the labels. Is this possible?

Thanks.

解决方案

Actually both linked questions provide a way how to achieve the desired result.

The easiest method is to create as many scatter plots as unique classes exist and give each a single color and legend entry.

import matplotlib.pyplot as plt

x=[1,2,3,4]
y=[5,6,7,8]
classes = [2,4,4,2]
unique = list(set(classes))
colors = [plt.cm.jet(float(i)/max(unique)) for i in unique]
for i, u in enumerate(unique):
    xi = [x[j] for j  in range(len(x)) if classes[j] == u]
    yi = [y[j] for j  in range(len(x)) if classes[j] == u]
    plt.scatter(xi, yi, c=colors[i], label=str(u))
plt.legend()

plt.show()

In case the classes are string labels, the solution would look slightly different, in that you need to get the colors from their index instead of using the classes themselves.

import numpy as np
import matplotlib.pyplot as plt

x=[1,2,3,4]
y=[5,6,7,8]
classes = ['X','Y','Z','X']
unique = np.unique(classes)
colors = [plt.cm.jet(i/float(len(unique)-1)) for i in range(len(unique))]
for i, u in enumerate(unique):
    xi = [x[j] for j  in range(len(x)) if classes[j] == u]
    yi = [y[j] for j  in range(len(x)) if classes[j] == u]
    plt.scatter(xi, yi, c=colors[i], label=str(u))
plt.legend()

plt.show()

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