极客笔记将 matplotlib 图例放置在图形外部
参考：matplotlib legend outside figure
在Matplotlib中，我们可以很容易地将图例（legend）放置在图形外部。这在需要更灵活地控制图例位置时非常有用。接下来，我们将介绍如何在Matplotlib中将图例放置在图形外部。
首先，我们需要导入Matplotlib库：
import matplotlib.pyplot as plt
将图例放置在图形外部
要将图例放置在图形外部，我们可以使用bbox_to_anchor参数来控制图例的位置。该参数接受一个包含四个值的元组，分别表示图例的左下角在图形坐标系中的位置。
下面是一个简单的示例代码，将图例放置在图形右上方：
import matplotlib.pyplot as plt
x = [1, 2, 3, 4, 5]
y = [10, 15, 13, 18, 16]
plt.plot(x, y, label='Line 1')
plt.legend(loc='upper right', bbox_to_anchor=(1.3, 1))
plt.show()
Output:
在上面的示例中，我们使用loc='upper right'将图例放置在右上角，然后使用bbox_to_anchor=(1.3, 1)将图例稍微向右移动。你可以根据需要调整bbox_to_anchor参数的值来进一步调整图例的位置。
示例代码
示例1：将图例放置在图形右下方
import matplotlib.pyplot as plt
x = [1, 2, 3, 4, 5]
y = [10, 15, 13, 18, 16]
plt.plot(x, y, label='Line 1')
plt.legend(loc='lower right', bbox_to_anchor=(1.3, 0))
plt.show()
Output:
示例2：将图例放置在图形左上方
import matplotlib.pyplot as plt
x = [1, 2, 3, 4, 5]
y = [10, 15, 13, 18, 16]
plt.plot(x, y, label='Line 1')
plt.legend(loc='upper left', bbox_to_anchor=(-0.3, 1))
plt.show()
Output:
示例3：将图例放置在图形左下方
import matplotlib.pyplot as plt
x = [1, 2, 3, 4, 5]
y = [10, 15, 13, 18, 16]
plt.plot(x, y, label='Line 1')
plt.legend(loc='lower left', bbox_to_anchor=(-0.3, 0))
plt.show()
Output:
示例4：将图例放置在图形顶部中央
import matplotlib.pyplot as plt
x = [1, 2, 3, 4, 5]
y = [10, 15, 13, 18, 16]
plt.plot(x, y, label='Line 1')
plt.legend(loc='upper center', bbox_to_anchor=(0.5, 1))
plt.show()
Output:
示例5：将图例放置在图形底部中央
import matplotlib.pyplot as plt
x = [1, 2, 3, 4, 5]
y = [10, 15, 13, 18, 16]
plt.plot(x, y, label='Line 1')
plt.legend(loc='lower center', bbox_to_anchor=(0.5, 0))
plt.show()
Output:
示例6：将图例放置在图形右侧中央
import matplotlib.pyplot as plt
x = [1, 2, 3, 4, 5]
y = [10, 15, 13, 18, 16]
plt.plot(x, y, label='Line 1')
plt.legend(loc='center right', bbox_to_anchor=(1.3, 0.5))
plt.show()
Output:
示例7：将图例放置在图形左侧中央
import matplotlib.pyplot as plt
x = [1, 2, 3, 4, 5]
y = [10, 15, 13, 18, 16]
plt.plot(x, y, label='Line 1')
plt.legend(loc='center left', bbox_to_anchor=(-0.3, 0.5))
plt.show()
Output:
示例8：将图例放置在图形中央
import matplotlib.pyplot as plt
x = [1, 2, 3, 4, 5]
y = [10, 15, 13, 18, 16]
plt.plot(x, y, label='Line 1')
plt.legend(loc='center', bbox_to_anchor=(0.5, 0.5))
plt.show()
Output:
示例9：将图例放置在图形右上方并且分散对齐
import matplotlib.pyplot as plt
x = [1, 2, 3, 4, 5]
y = [10, 15, 13, 18, 16]
plt.plot(x, y, label='Line 1')
plt.legend(loc='upper right', bbox_to_anchor=(1.3, 1), mode='expand', ncol=2)
plt.show()
Output:
示例10：将图例放置在图形左下方并且分散对齐
import matplotlib.pyplot as plt
x = [1, 2, 3, 4, 5]
y = [10, 15, 13, 18, 16]
plt.plot(x, y, label='Line 1')
plt.legend(loc='lower left', bbox_to_anchor=(-0.3, 0), mode='expand', ncol=2)
plt.show()
Output:
示例11：将图例放置在图形底部中央并且分散对齐
import matplotlib.pyplot as plt
x = [1, 2, 3, 4, 5]
y = [10, 15, 13, 18, 16]
plt.plot(x, y, label='Line 1')
plt.legend(loc='lower center', bbox_to_anchor=(0.5, 0), mode='expand', ncol=2)
plt.show()
Output:
示例12：将图例放置在图形右侧中央并且分散对齐
import matplotlib.pyplot as plt
x = [1, 2, 3, 4, 5]
y = [10, 15, 13, 18, 16]
plt.plot(x, y, label='Line 1')
plt.legend(loc='center right', bbox_to_anchor=(1.3, 0.5), mode='expand', ncol=2)
plt.show()
Output:
示例13：将图例放置在图形左侧中央并且分散对齐
import matplotlib.pyplot as plt
x = [1, 2, 3, 4, 5]
y = [10, 15, 13, 18, 16]
plt.plot(x, y, label='Line 1')
plt.legend(loc='center left', bbox_to_anchor=(-0.3, 0.5), mode='expand', ncol=2)
plt.show()
Output:
示例14：将图例放置在图形中央并且分散对齐
import matplotlib.pyplot as plt
x = [1, 2, 3, 4, 5]
y = [10, 15, 13, 18, 16]
plt.plot(x, y, label='Line 1')
plt.legend(loc='center', bbox_to_anchor=(0.5, 0.5), mode='expand', ncol=2)
plt.show()
Output:
总结
通过以上示例，我们学会了如何在Matplotlib中将图例放置在图形外部，并且通过调整bbox_to_anchor参数可以灵活控制图例的位置。