python matplotlib如何将图例放在图外

叁歲伎倆 2022-09-29 01:56 225阅读 0赞

原文地址：http://blog.csdn.net/john\_xyz/article/details/54754937

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()
     
      
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运行结果如下   
![这里写图片描述][SouthEast]   
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()
     
      
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![这里写图片描述][SouthEast 1]   
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()
     
      
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![这里写图片描述][SouthEast 2]

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。

关于plt.legend更多的参数信息，详细见官方文档：[http://matplotlib.org/api/pyplot\_api.html\#matplotlib.pyplot.legend][http_matplotlib.org_api_pyplot_api.html_matplotlib.pyplot.legend]   
关于legend的官方教程：详细见：[http://matplotlib.org/users/legend\_guide.html][http_matplotlib.org_users_legend_guide.html]   
关于pandas.DataFrame.plot更多的作图问题，详细见：[http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.plot.html][http_pandas.pydata.org_pandas-docs_stable_generated_pandas.DataFrame.plot.html]

[SouthEast]: /images/20220708/322029791d7e4cea8df98e7c4e684d1d.png
[SouthEast 1]: /images/20220708/6b63659fb3bd48db81ad7607fdd56e94.png
[SouthEast 2]: /images/20220708/aa8772d1f3b542f688ffeb6d5c42e3d2.png
[http_matplotlib.org_api_pyplot_api.html_matplotlib.pyplot.legend]: http://matplotlib.org/api/pyplot_api.html#matplotlib.pyplot.legend
[http_matplotlib.org_users_legend_guide.html]: http://matplotlib.org/users/legend_guide.html
[http_pandas.pydata.org_pandas-docs_stable_generated_pandas.DataFrame.plot.html]: http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.plot.html