Bug report

Changing plot alignment for different placing of colorbar() in twinx plot

If one combines a pcolormesh plot/hist2d plot with a standard plot by using twinx, the graph from the plot moves to wrong x values if the colorbar is called after the plot call. If it is called before, the alignment is fine.

I am not sure if this is a bug or just wrong usage.
However, one of the resulting graphs has a wrong extent that might lead to misinterpretations.

Code for reproduction

import numpy as np
import matplotlib.pyplot as plt

data = np.random.random((64, 128)) * 2.0
x = np.arange(128)
y = np.arange(64)
plt.pcolormesh(x, y, data)

#plt.colorbar() --> here it works fine
plt.twinx()
plt.colorbar()
# --> here it gives wrong x values for the orange plot

plt.plot(x, np.sin(x/10), color="orange", lw=4)

plt.show()

Actual outcome

Next to the confusing layout the plot shows actually a wrong graph:
the orange plot just goes to around x=100 but should go to x=128.
(The axis of the colorbar is correct and shows the range of data.)

Expected outcome

If colorbar is called before twinx, the orange graph has the correct extent.

I am not sure if this is a bug or a wrong usage of matplotlib. In any case the wrong extent of the (in this case) orange plot is a dangerous behavior that might lead to misinterpretations of the data.

Matplotlib version

• Operating System: Ubuntu 14.04.1
• Matplotlib Version: 2.0.0rc1
• Python Version: 3.4.3
• Jupyter Version: 1.0.0 (I am using %matplotlib inline)
• Other Libraries: numpy 1.12.0b1

I installed matplotlib via pip.