How share x axis of two subplots after they are created? : <p>I'm trying to share two subplots axis, but I need to share x axis after the figure was created.
So, for instance, I create this figure:</p>

<pre><code>import numpy as np
import matplotlib.pyplot as plt

t= np.arange(1000)/100.
x = np.sin(2*np.pi*10*t)
y = np.cos(2*np.pi*10*t)

fig=plt.figure()
ax1 = plt.subplot(211)
plt.plot(t,x)
ax2 = plt.subplot(212)
plt.plot(t,y)

# some code to share both x axis

plt.show()
</code></pre>

<p>Instead of the comment I would insert some code to share both x axis.
I didn't find any clue how i can do that. There are some attributes 
<code>_shared_x_axes</code> and <code>_shared_x_axes</code> when i check to figure axis (<code>fig.get_axes()</code>) but I don't know how to link them.</p>
