python-增加matplotlib中图例行的线宽

我知道，如果更改线的线宽，则会在图例中自动更新。但是，我只想更改图例的线宽而不影响绘图。

4个解决方案

62 votes

这是一个简单的例子：

import numpy as np

import matplotlib.pyplot as plt

# make some data

x = np.linspace(0, 2*np.pi)

y1 = np.sin(x)

y2 = np.cos(x)

# plot sin(x) and cos(x)

p1 = plt.plot(x, y1, 'b-', linewidth=1.0)

p2 = plt.plot(x, y2, 'r-', linewidth=1.0)

# make a legend for both plots

leg = plt.legend([p1, p2], ['sin(x)', 'cos(x)'], loc=1)

# set the linewidth of each legend object

for legobj in leg.legendHandles:

legobj.set_linewidth(2.0)

plt.show()

Brendan Wood answered 2020-02-09T02:58:01Z

6 votes

@Brendan Wood的方法使用pyplot提供的api。在matplotlib中，首选使用轴的面向对象样式。 下面是如何使用axes方法实现此目的的方法。

import numpy as np

import matplotlib.pyplot as plt

# make some data

x = np.linspace(0, 2*np.pi)

y1 = np.sin(x)

y2 = np.cos(x)

fig, ax = plt.subplots()

ax.plot(x, y1, linewidth=1.0, label='sin(x)')

ax.plot(x, y2, linewidth=1.0, label='cos(x)')

leg = ax.legend()

for line in leg.get_lines():

line.set_linewidth(4.0)

plt.show()

生成的图如下所示，

jdhao answered 2020-02-09T02:58:28Z

3 votes

如果要更改绘图中的所有线条，定义自己的图例处理程序可能会很有用：

import matplotlib.pyplot as plt

from matplotlib import legend_handler

from matplotlib.lines import Line2D

import numpy as np

class MyHandlerLine2D(legend_handler.HandlerLine2D):

def create_artists(self, legend, orig_handle,

xdescent, ydescent, width, height, fontsize,

trans):

xdata, xdata_marker = self.get_xdata(legend, xdescent, ydescent,

width, height, fontsize)

ydata = ((height-ydescent)/2.)*np.ones(xdata.shape, float)

legline = Line2D(xdata, ydata)

self.update_prop(legline, orig_handle, legend)

#legline.update_from(orig_handle)

#legend._set_artist_props(legline) # after update

#legline.set_clip_box(None)

#legline.set_clip_path(None)

legline.set_drawstyle('default')

legline.set_marker("")

legline.set_linewidth(10)

legline_marker = Line2D(xdata_marker, ydata[:len(xdata_marker)])

self.update_prop(legline_marker, orig_handle, legend)

#legline_marker.update_from(orig_handle)

#legend._set_artist_props(legline_marker)

#legline_marker.set_clip_box(None)

#legline_marker.set_clip_path(None)

legline_marker.set_linestyle('None')

if legend.markerscale != 1:

newsz = legline_marker.get_markersize()*legend.markerscale

legline_marker.set_markersize(newsz)

# we don't want to add this to the return list because

# the texts and handles are assumed to be in one-to-one

# correpondence.

legline._legmarker = legline_marker

return [legline, legline_marker]

plt.plot( [0, 1], [0, 1], '-r', lw=1, label='Line' )

plt.legend(handler_map={Line2D:MyHandlerLine2D()})

plt.show()

David Zwicker answered 2020-02-09T02:58:48Z

3 votes

默认情况下，图例包含行本身。 因此，更改画布中线条的线宽也会更改图例中的线条(反之亦然，因为它们本质上是同一对象)。

一种可能的解决方案是使用画布上艺术家的副本，并仅更改副本的线宽。

import numpy as np

import matplotlib.pyplot as plt

import copy

x = np.linspace(0, 2*np.pi)

y1 = np.sin(x)

y2 = np.cos(x)

fig = plt.figure()

ax = fig.add_subplot(111)

ax.plot(x, y1, c='b', label='y1',linewidth=1.0)

ax.plot(x, y2, c='r', label='y2')

# obtain the handles and labels from the figure

handles, labels = ax.get_legend_handles_labels()

# copy the handles

handles = [copy.copy(ha) for ha in handles ]

# set the linewidths to the copies

[ha.set_linewidth(7) for ha in handles ]

# put the copies into the legend

leg = plt.legend(handles=handles, labels=labels)

plt.savefig('leg_example')

plt.show()

另一种选择是使用handler_map和更新功能。 这以某种方式是自动的，指定处理程序映射将自动使图例中的任何行宽7点。

import numpy as np

import matplotlib.pyplot as plt

from matplotlib.legend_handler import HandlerLine2D

x = np.linspace(0, 2*np.pi)

y1 = np.sin(x)

y2 = np.cos(x)

fig = plt.figure()

ax = fig.add_subplot(111)

ax.plot(x, y1, c='b', label='y1',linewidth=1.0)

ax.plot(x, y2, c='r', label='y2')

linewidth=7

def update(handle, orig):

handle.update_from(orig)

handle.set_linewidth(7)

plt.legend(handler_map={plt.Line2D : HandlerLine2D(update_func=update)})

plt.show()

结果与上面相同。

ImportanceOfBeingErnest answered 2020-02-09T02:59:22Z