python-pyplot庫中legend函數即參數使用

1.圖例legend基礎語法及用法

 

legend語法參數如下: matplotlib.pyplot.legend(*args, **kwargs)

Keyword	Description
loc	Location code string, or tuple (see below).圖例所有figure位置
prop	the font property字體參數
fontsize	the font size (used only if prop is not specified)
markerscale	the relative size of legend markers vs. original 圖例標記與原始標記的相對大小
markerfirst	If True (default), marker is to left of the label. 如果為True，則圖例標記位於圖例標簽的左側
numpoints	the number of points in the legend for line 為線條圖圖例條目創建的標記點數
scatterpoints	the number of points in the legend for scatter plot 為散點圖圖例條目創建的標記點數
scatteryoffsets	a list of yoffsets for scatter symbols in legend 為散點圖圖例條目創建的標記的垂直偏移量
frameon	If True, draw the legend on a patch (frame). 控制是否應在圖例周圍繪制框架
fancybox	If True, draw the frame with a round fancybox. 控制是否應在構成圖例背景的FancyBboxPatch周圍啟用圓邊
shadow	If True, draw a shadow behind legend. 控制是否在圖例后面畫一個陰影
framealpha	Transparency of the frame. 控制圖例框架的 Alpha 透明度
edgecolor	Frame edgecolor.
facecolor	Frame facecolor.
ncol	number of columns 設置圖例分為n列展示
borderpad	the fractional whitespace inside the legend border 圖例邊框的內邊距
labelspacing	the vertical space between the legend entries 圖例條目之間的垂直間距
handlelength	the length of the legend handles  圖例句柄的長度
handleheight	the height of the legend handles  圖例句柄的高度
handletextpad	the pad between the legend handle and text  圖例句柄和文本之間的間距
borderaxespad	the pad between the axes and legend border 軸與圖例邊框之間的距離
columnspacing	the spacing between columns 列間距
title	the legend title
bbox_to_anchor	the bbox that the legend will be anchored.指定圖例在軸的位置
bbox_transform	the transform for the bbox. transAxes if None.

 

 

 

(1)設置圖例位置

使用loc參數

plt.legend(loc='lower left')

0: ‘best' 1: ‘upper right' 2: ‘upper left' 3: ‘lower left'

4: ‘lower right' 5: ‘right' 6: ‘center left'

7: ‘center right' 8: ‘lower center' 9: ‘upper center' 10: ‘center'

 

(2)設置圖例字體

#設置字體大小

fontsize : int or float or {‘xx-small’, ‘x-small’, ‘small’, ‘medium’, ‘large’, ‘x-large’, ‘xx-large’}

 

(3)設置圖例邊框及背景

plt.legend(loc='best',frameon=False) #去掉圖例邊框

plt.legend(loc='best',edgecolor='blue') #設置圖例邊框顏色

plt.legend(loc='best',facecolor='blue') #設置圖例背景顏色,若無邊框,參數無效

 

(4)設置圖例標題

plt.legend(loc='best',title='figure 1 legend') #去掉圖例邊框

2.legend面向對象命令

(1)獲取並設置legend圖例       
plt.legend(loc=0, numpoints=1)
leg = plt.gca().get_legend() #或leg=ax.get_legend()
ltext = leg.get_texts()
plt.setp(ltext, fontsize=12,fontweight='bold') 

(2)設置圖例
legend = ax.legend((rectsTest1, rectsTest2, rectsTest3), ('test1', 'test2', 'test3'))  
legend = ax.legend(loc='upper center', shadow=True, fontsize='x-large')
legend.get_frame().set_facecolor('red') #設置圖例legend背景為紅色
frame = legend.get_frame()  
frame.set_alpha(1)  
frame.set_facecolor('none')  #設置圖例legend背景透明  

(3)移除圖例
ax1.legend_.remove() ##移除子圖ax1中的圖例
ax2.legend_.remove() ##移除子圖ax2中的圖例
ax3.legend_.remove() ##移除子圖ax3中的圖例

3.案例：設置圖例legend到圖形邊界外

1. #主要是bbox_to_anchor的使用

2. box = ax1.get_position()

3. ax1.set_position([box.x0, box.y0, box.width , box.height* 0.8])

4. ax1.legend(loc='center', bbox_to_anchor=(0.5, 1.2),ncol=3)

 

 

4.案例：顯示多圖例legend

1. import matplotlib.pyplot as plt

2. import numpy as np

3. x = np.random.uniform(-1, 1, 4)

4. y = np.random.uniform(-1, 1, 4)

5. p1, = plt.plot([1,2,3])

6. p2, = plt.plot([3,2,1])

7. l1 = plt.legend([p2, p1], ["line 2", "line 1"], loc='upper left')

8.  

9. p3 = plt.scatter(x[0:2], y[0:2], marker = 'D', color='r')

10. p4 = plt.scatter(x[2:], y[2:], marker = 'D', color='g')

11. # This removes l1 from the axes.

12. plt.legend([p3, p4], ['label', 'label1'], loc='lower right', scatterpoints=1)

13. # Add l1 as a separate artist to the axes

14. plt.gca().add_artist(l1)

 

1. import matplotlib.pyplot as plt

2. line1, = plt.plot([1,2,3], label="Line 1", linestyle='--')

3. line2, = plt.plot([3,2,1], label="Line 2", linewidth=4)

4. # 為第一個線條創建圖例

5. first_legend = plt.legend(handles=[line1], loc=1)

6. # 手動將圖例添加到當前軸域

7. ax = plt.gca().add_artist(first_legend)

8. # 為第二個線條創建另一個圖例

9. plt.legend(handles=[line2], loc=4)

10. plt.show()