Matplotlib.pyplot:如何为现有绘图设置第二个y轴

时间:2016-03-19 16:35:08

标签: python matplotlib bar-chart

我有两组线性相关的值。因此,我只需要一个具有正确比例的第二个y轴的单个图形。

  

最优雅的方法是什么?

只制作两个条形图给我一个重叠:

import numpy as np
import matplotlib.pyplot as plt 

x = np.arange(4)
y2 = np.array([23, 32, 24, 28])
y1 = 4.2 * y2

fig = plt.figure(1, figsize=(6,6))

ax = fig.add_subplot(111)
ax.bar(x, y2) 
ax.set_ylabel('Consumption in $m^3$')
ax2 = ax.twinx()
ax2.bar(x, y1, alpha=0.5) 
ax2.set_ylabel('Consumption in EUR')

plt.savefig('watercomsumption.png', format='png', bbox_inches="tight")

example-plot

非常感谢! : - )

修改

我可能不清楚。我想制作一个单个图表。 像下面这样的东西。但有没有比调用条形函数两次并用alpha=0隐藏它更优雅的方式?

import numpy as np
import matplotlib.pyplot as plt

x = np.arange(4)
y2 = np.array([23, 32, 24, 28])
y1 = 4.2 * y2

y2max = np.max(y2) * 1.1

fig = plt.figure(1, figsize=(6,6))

ax = fig.add_subplot(111)
ax.bar(x, y2)
ax.set_ylabel('Consumption in $m^3$')
ax2 = ax.twinx()

ax2.bar(x, y1, alpha=0)
ax2.set_ylabel('Consumption in EUR')

ax.set_ylim(ymax=y2max)
ax2.set_ylim(ymax=4.2*y2max)

plt.savefig('watercomsumption.png', format='png', bbox_inches="tight")

example-code2

1 个答案:

答案 0 :(得分:5)

如果您不想两次拨打bar并且只想让第二个y轴提供转换,那么第二次根本不要再调用bar。您仍然可以创建和调整第二个y轴,而实际上可以在其上绘制任何内容。

import numpy as np
import matplotlib.pyplot as plt

x = np.arange(4)
y2 = np.array([23, 32, 24, 28])
y1 = 4.2 * y2

y2max = np.max(y2) * 1.1

fig = plt.figure(1, figsize=(6,6))

ax = fig.add_subplot(111)
ax.bar(x, y2)
ax.set_ylabel('Consumption in $m^3$')
ax2 = ax.twinx()

ax2.set_ylabel('Consumption in EUR')

ax.set_ylim(ymax=y2max)
ax2.set_ylim(ymax=4.2*y2max)

enter image description here