python matplotlib实现将图例放在图外

  • Z时代
  • 2024-01-10
  • 分类：综合

关于matplotlib如何设置图例的位置？如何将图例放在图外？以及如何在一幅图有多个子图的情况下，删除重复的图例？我用一个简单的例子说明一下。

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
fig = plt.figure(1)
ax1 = fig.add_subplot(2,2,1)
ax2 = fig.add_subplot(2,2,2)
ax3 = fig.add_subplot(2,2,3)
ax4 = fig.add_subplot(2,2,4)
df1 = pd.DataFrame(np.random.randn(3,5),columns = ['one','two','three','four','five'])
df2 = pd.DataFrame(np.random.randn(3,5),columns = ['one','two','three','four','five'])
df3 = pd.DataFrame(np.random.randn(3,5),columns = ['one','two','three','four','five'])
df4 = pd.DataFrame(np.random.randn(3,5),columns = ['one','two','three','four','five'])
df1.plot(ax = ax1, title = "df1", grid = 'on')
df2.plot(ax = ax2, title = "df1", grid = 'on')
df3.plot(ax = ax3, title = "df1", grid = 'on')
df4.plot(ax = ax4, title = "df1", grid = 'on')
plt.show()

运行结果如下

可以看出，随机生成了几个dataframe,在一个figure()中生成了四个子图，每个子图的图例都是dataframe.columns里的值，那么如何移除这些图例？

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
fig = plt.figure(1)
ax1 = fig.add_subplot(2,2,1)
ax2 = fig.add_subplot(2,2,2)
ax3 = fig.add_subplot(2,2,3)
ax4 = fig.add_subplot(2,2,4)
df1 = pd.DataFrame(np.random.randn(3,5),columns = ['one','two','three','four','five'])
df2 = pd.DataFrame(np.random.randn(3,5),columns = ['one','two','three','four','five'])
df3 = pd.DataFrame(np.random.randn(3,5),columns = ['one','two','three','four','five'])
df4 = pd.DataFrame(np.random.randn(3,5),columns = ['one','two','three','four','five'])
df1.plot(ax = ax1, title = "df1", grid = 'on')
df2.plot(ax = ax2, title = "df1", grid = 'on')
df3.plot(ax = ax3, title = "df1", grid = 'on')
df4.plot(ax = ax4, title = "df1", grid = 'on')
ax1.legend_.remove()  ##移除子图ax1中的图例
ax2.legend_.remove()  ##移除子图ax2中的图例
ax3.legend_.remove()  ##移除子图ax3中的图例
plt.show()

可以看出ax1,ax2,ax3中的图例都被移除了，但是上图还不是很美观？有没有什么办法将图例放到图外面呢？请看:

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
fig = plt.figure(1)
ax1 = fig.add_subplot(2,2,1)
ax2 = fig.add_subplot(2,2,2)
ax3 = fig.add_subplot(2,2,3)
ax4 = fig.add_subplot(2,2,4)
df1 = pd.DataFrame(np.random.randn(3,5),columns = ['one','two','three','four','five'])
df2 = pd.DataFrame(np.random.randn(3,5),columns = ['one','two','three','four','five'])
df3 = pd.DataFrame(np.random.randn(3,5),columns = ['one','two','three','four','five'])
df4 = pd.DataFrame(np.random.randn(3,5),columns = ['one','two','three','four','five'])
df1.plot(ax = ax1, title = "df1", grid = 'on')
df2.plot(ax = ax2, title = "df1", grid = 'on')
df3.plot(ax = ax3, title = "df1", grid = 'on')
df4.plot(ax = ax4, title = "df1", grid = 'on')
ax1.legend_.remove()
ax2.legend_.remove()
ax3.legend_.remove()
ax4.legend(loc=2, bbox_to_anchor=(1.05,1.0),borderaxespad = 0.)  ##设置ax4中legend的位置，将其放在图外
plt.show()

其中参数loc用于设置legend的位置

bbox_to_anchor用于在bbox_transform坐标（默认轴坐标）中为图例指定任意位置。

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