带有 twinx() 的辅助轴:如何添加到图例中? [英] Secondary axis with twinx(): how to add to legend?

问题描述

我有一个带有两个 y 轴的图，使用 twinx().我也给线条加上标签，想用 legend() 显示它们，但我只成功获得了图例中一个轴的标签:

I have a plot with two y-axes, using twinx(). I also give labels to the lines, and want to show them with legend(), but I only succeed to get the labels of one axis in the legend:

import numpy as np
import matplotlib.pyplot as plt
from matplotlib import rc
rc('mathtext', default='regular')

fig = plt.figure()
ax = fig.add_subplot(111)
ax.plot(time, Swdown, '-', label = 'Swdown')
ax.plot(time, Rn, '-', label = 'Rn')
ax2 = ax.twinx()
ax2.plot(time, temp, '-r', label = 'temp')
ax.legend(loc=0)
ax.grid()
ax.set_xlabel("Time (h)")
ax.set_ylabel(r"Radiation ($MJ,m^{-2},d^{-1}$)")
ax2.set_ylabel(r"Temperature ($^circ$C)")
ax2.set_ylim(0, 35)
ax.set_ylim(-20,100)
plt.show()

所以我只得到图例中第一个轴的标签，而不是第二个轴的标签temp".我如何将这第三个标签添加到图例中?

So I only get the labels of the first axis in the legend, and not the label 'temp' of the second axis. How could I add this third label to the legend?

推荐答案

您可以通过添加以下行轻松添加第二个图例:

You can easily add a second legend by adding the line:

ax2.legend(loc=0)

你会得到这个:

但是，如果您想将所有标签放在一个图例上，那么您应该执行以下操作:

But if you want all labels on one legend then you should do something like this:

import numpy as np
import matplotlib.pyplot as plt
from matplotlib import rc
rc('mathtext', default='regular')

time = np.arange(10)
temp = np.random.random(10)*30
Swdown = np.random.random(10)*100-10
Rn = np.random.random(10)*100-10

fig = plt.figure()
ax = fig.add_subplot(111)

lns1 = ax.plot(time, Swdown, '-', label = 'Swdown')
lns2 = ax.plot(time, Rn, '-', label = 'Rn')
ax2 = ax.twinx()
lns3 = ax2.plot(time, temp, '-r', label = 'temp')

# added these three lines
lns = lns1+lns2+lns3
labs = [l.get_label() for l in lns]
ax.legend(lns, labs, loc=0)

ax.grid()
ax.set_xlabel("Time (h)")
ax.set_ylabel(r"Radiation ($MJ,m^{-2},d^{-1}$)")
ax2.set_ylabel(r"Temperature ($^circ$C)")
ax2.set_ylim(0, 35)
ax.set_ylim(-20,100)
plt.show()

哪个会给你这个:

这篇关于带有 twinx() 的辅助轴:如何添加到图例中?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！