使用多色线向 matplotlib 图中添加图例 [英] Adding a legend to a matplotlib plot with a multicolored line

问题描述

按照

解决方案

这个想法也是在图例中显示一个线集合.没有内置的方法可以做到这一点，但可以将 HandlerLineCollection 子类化并在其 create_artists 方法中创建相应的 LineCollection.

将 numpy 导入为 np导入matplotlib.pyplot作为plt从 matplotlib.legend_handler 导入 HandlerLineCollection从matplotlib.collections导入LineCollection类 HandlerColorLineCollection(HandlerLineCollection):def create_artists(自我，传奇，艺术家，xdescent，ydescent，宽度，高度，字体大小，trans):x = np.linspace(0,width,self.get_numpoints(legend)+1)y = np.zeros(self.get_numpoints(legend)+1)+ height/2.-ydescentpoints = np.array([x，y]).T.reshape(-1，1，2)segment = np.concatenate([points[:-1], points[1:]],axis=1)lc = LineCollection(段，cmap = artist.cmap，变换=反式)lc.set_array(x)lc.set_linewidth(artist.get_linewidth())返回 [lc]t = np.linspace(0, 10, 200)x = np.cos(np.pi * t)y = np.sin(t)points = np.array([x，y]).T.reshape(-1，1，2)segment = np.concatenate([points[:-1], points[1:]],axis=1)lc = LineCollection(段，cmap = plt.get_cmap('copper')，norm=plt.Normalize(0, 10), linewidth=3)lc.set_array(t)无花果，ax = plt.subplots()ax.add_collection(lc)plt.legend([lc]，["test"]，\handler_map={lc: HandlerColorLineCollection(numpoints=4)}, framealpha=1)ax.autoscale_view()plt.show()

Following the example on how to draw multicolored lines I can draw lines that change color along their length based on some color map. Trying to add a legend to the plot I added this code:

plt.legend([lc], ["test"],\
    handler_map={lc: matplotlib.legend_handler.HandlerLineCollection()})

This adds a legend to the plot (figure below) but the color of the icon in the legend does not relate at all to the colors of the line. Is this the wrong way to try to add a legend to this plot, or is this a limitation of matplotlib?

解决方案

The idea would be to show a line collection in the legend as well. There is no inbuilt way to do that but one may subclass HandlerLineCollection and create the respective LineCollection within its create_artists method.

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.legend_handler import HandlerLineCollection
from matplotlib.collections import LineCollection

class HandlerColorLineCollection(HandlerLineCollection):
    def create_artists(self, legend, artist ,xdescent, ydescent,
                        width, height, fontsize,trans):
        x = np.linspace(0,width,self.get_numpoints(legend)+1)
        y = np.zeros(self.get_numpoints(legend)+1)+height/2.-ydescent
        points = np.array([x, y]).T.reshape(-1, 1, 2)
        segments = np.concatenate([points[:-1], points[1:]], axis=1)
        lc = LineCollection(segments, cmap=artist.cmap,
                     transform=trans)
        lc.set_array(x)
        lc.set_linewidth(artist.get_linewidth())
        return [lc]

t = np.linspace(0, 10, 200)
x = np.cos(np.pi * t)
y = np.sin(t)
points = np.array([x, y]).T.reshape(-1, 1, 2)
segments = np.concatenate([points[:-1], points[1:]], axis=1)

lc = LineCollection(segments, cmap=plt.get_cmap('copper'),
                    norm=plt.Normalize(0, 10), linewidth=3)
lc.set_array(t)

fig, ax = plt.subplots()
ax.add_collection(lc)

plt.legend([lc], ["test"],\
    handler_map={lc: HandlerColorLineCollection(numpoints=4)}, framealpha=1)

ax.autoscale_view()
plt.show()

这篇关于使用多色线向 matplotlib 图中添加图例的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！