具有不同端点标记的线的图例

Question

我需要为线段创建一个图例，该线段在该线的底部和顶部具有不同的标记。 我能够创建一个图例，其中重复了 1 个标记符号，但不能在每一端创建两个不同的标记。

这是一个可重现的示例。

from matplotlib import pyplot as plt
import numpy as np

#Create some data
x = np.arange(0,11)
y1 = np.sqrt(x/2.)
y2 = x


plt.figure(figsize=(8,8))
ax = plt.subplot(111)

#Plot the lines
for i,x_ in zip(range(11),x):
    ax.plot([x_,x_],[y1[i],y2[i]],c='k')
    
#Plot the end points    
ax.scatter(x,y1,marker='s',c='r',s=100,zorder=10)
ax.scatter(x,y2,marker='o',c='r',s=100,zorder=10)

ax.plot([],[],c='k',marker='o',mfc='r',label='Test Range') #Create a single line for the label
ax.legend(loc=2,numpoints=2,prop={'size':16}) # How can I add a label with different symbols the line segments?

plt.show()

最终产品应该有一个带有符号的图例，该符号显示连接圆形和正方形的线。

Answer 1

恐怕您必须组合不同的mpatches补丁，我不确定是否有更好的解决方案

import matplotlib.pyplot as plt
import numpy as np
import matplotlib.patches as mpatches
from matplotlib.legend_handler import HandlerPatch
from matplotlib.legend_handler import HandlerLine2D


class HandlerCircle(HandlerPatch):
    def create_artists(self,legend,orig_handle,
                       xdescent,ydescent,width,height,fontsize,trans):
        center = 0.5 * width, 0.5 * height
        p = mpatches.Circle(xy=center,radius=width*0.3) 
        self.update_prop(p,orig_handle,legend)
        p.set_transform(trans)
        return [p]
    
class HandlerRectangle(HandlerPatch):
    def create_artists(self, legend, orig_handle,
                       xdescent, ydescent, width, height, fontsize, trans):
        center = 0,height/2-width*0.5/2
        width,height = width*0.5,width*0.5
        p = mpatches.Rectangle(xy=center,width=width,height=width) 
        self.update_prop(p, orig_handle, legend)
        p.set_transform(trans)
        return [p]

fig,ax = plt.subplots(figsize=(12,8))
texts = ['','','Test Range']
line, = ax.plot([],[],c='k')
c = [mpatches.Circle((0.,0.,),facecolor='r',linewidth=.5),
     line,
     mpatches.Rectangle((0.,0.),5,5,facecolor='r',linewidth=.5)]

ax.legend(c,texts,bbox_to_anchor=(.25,.95),loc='center',ncol=3,prop={'size':20},
          columnspacing=-1,handletextpad=.6,
          handler_map={mpatches.Circle: HandlerCircle(), 
                       line: HandlerLine2D(numpoints=0,),
                       mpatches.Rectangle: HandlerRectangle()}).get_frame().set_facecolor('w')

plt.show()

运行这个脚本，你会得到

如果您使用不同的图形大小或不同的图例大小，我上面脚本中的设置可能不是最佳的。 在这种情况下，您可以调整以下参数：

1. Circle和Rectangle的中心和大小
2. columnspacing ax.legend(...)中的ax.legend(...) columnspacing和handletextpad