Multiple y-scales but only one enabled for pan and

Question

Consider the following python code for plotting a matplotlib figure:

import matplotlib.pylab as pp
import numpy as np

alpha = np.linspace(0, 2 * np.pi, 400)
sig1 = np.sin(alpha)
sig2 = np.sin(2 * alpha) + 2 * (alpha > np.pi)

ax1 = pp.subplot(111)
ax2 = ax1.twinx()

ax1.plot(alpha, sig1, color='b')
ax2.plot(alpha, sig2, color='r')
ax1.set_ylabel('sig1 value', color='b')
ax2.set_ylabel('sig2 value', color='r')
pp.grid()
pp.show()

Giving me a nice plot

I would like to find out how to disable one of the axes for panning / zooming, so when I use the pan / zoom tool, only ax2 will rescale for example. Is there a way to do this? I want to do it programmatically.

Answer 1

You can do this using ax2.set_navigate(False):

from matplotlib.pyplot import *
import numpy as np

fig,ax1 = subplots(1,1)
ax2 = ax1.twinx()
ax2.set_navigate(False)
x = np.linspace(0,2*np.pi,100)
ax1.plot(x,np.sin(x),'b')
ax1.set_xlabel('Scaleable axis')
ax1.set_ylabel('Scaleable axis')
ax2.plot(x,np.sin(x+1),'r')
ax2.set_ylabel('Static axis',weight='bold')

Answer 2

A slightly more complex example with two plot areas and three vertical axes. Only the common horizontal axis and the left vertical axis of the lower subplot are interactive.

fig, ax_left = plt.subplots()
ax_right = ax_left.twinx()
ax_status = make_axes_locatable(ax_left).append_axes('top', size=1.2, pad=0., sharex=ax_left)
ax_status.xaxis.set_tick_params(labelbottom=False)
ax_right.set_navigate(False)
ax_status.set_navigate(False)

Before I added set_navigate(False) according to ali_m's answer, the two vertical axes of the lower plot were both affected by dragging the mouse vertically in the lower plot, while the status axis was unaffected as it should but only after the first mouse gesture. Dragging the mouse for the first time, all axes are affected. This seems to be a bug in matplotlib, just reported as #12613.