Matplotlib 圖例
Matplotlib 原生支援圖例。圖例可以放置在不同的位置：圖例可以放在圖表的內部或外部，並且可以移動位置。
legend() 方法將圖例新增到圖中。在本文中，我們將向你展示使用 Matplotlib 的一些圖例。
Matplotlib 內部圖例
要將圖例放在裡面，只需呼叫 legend()：
import matplotlib.pyplot as plt
import numpy as np
y = [2,4,6,8,10,12,14,16,18,20]
y2 = [10,11,12,13,14,15,16,17,18,19]
x = np.arange(10)
fig = plt.figure()
ax = plt.subplot(111)
ax.plot(x, y, label='$y = numbers')
ax.plot(x, y2, label='$y2 = other numbers')
plt.title('Legend inside')
ax.legend()
plt.show()
Matplotlib 底部圖例
要將圖例放在底部，請將 legend() 呼叫更改為：
ax.legend(loc='upper center', bbox_to_anchor=(0.5, -0.05), shadow=True, ncol=2)
ncol=2 將列數設定為 2 列，shadow=True 設定圖例會有陰影。
完整的程式碼是：
import matplotlib.pyplot as plt
import numpy as np
y = [2,4,6,8,10,12,14,16,18,20]
y2 = [10,11,12,13,14,15,16,17,18,19]
x = np.arange(10)
fig = plt.figure()
ax = plt.subplot(111)
ax.plot(x, y, label='$y = numbers')
ax.plot(x, y2, label='$y2 = other numbers')
plt.title('Legend inside')
ax.legend(loc='upper center', bbox_to_anchor=(0.5, -0.05), shadow=True, ncol=2)
plt.show()
Matplotlib 的頂部圖例
要將圖例置於頂部，請更改 bbox\_to\_anchor 值：
ax.legend(loc='upper center', bbox_to_anchor=(0.5, 1.00), shadow=True, ncol=2)
程式碼如下：
import matplotlib.pyplot as plt
import numpy as np
y = [2,4,6,8,10,12,14,16,18,20]
y2 = [10,11,12,13,14,15,16,17,18,19]
x = np.arange(10)
fig = plt.figure()
ax = plt.subplot(111)
ax.plot(x, y, label='$y = numbers')
ax.plot(x, y2, label='$y2 = other numbers')
plt.title('Legend inside')
ax.legend(loc='upper center', bbox_to_anchor=(0.5, 1.00), shadow=True, ncol=2)
plt.show()
Matplotlib 圖例放右側外部
我們可以通過調整框的大小來設定圖例，並將圖例放在圖的右側外部，
chartBox = ax.get_position()
ax.set_position([chartBox.x0, chartBox.y0, chartBox.width*0.6, chartBox.height])
ax.legend(loc='upper center', bbox_to_anchor=(1.45, 0.8), shadow=True, ncol=1)
程式碼：
import matplotlib.pyplot as plt
import numpy as np
y = [2,4,6,8,10,12,14,16,18,20]
y2 = [10,11,12,13,14,15,16,17,18,19]
x = np.arange(10)
fig = plt.figure()
ax = plt.subplot(111)
ax.plot(x, y, label='$y = numbers')
ax.plot(x, y2, label='$y2 = other numbers')
plt.title('Legend outside')
chartBox = ax.get_position()
ax.set_position([chartBox.x0, chartBox.y0, chartBox.width*0.6, chartBox.height])
ax.legend(loc='upper center', bbox_to_anchor=(1.45, 0.8), shadow=True, ncol=1)
plt.show()
