title: matplotlib: Unexpected gridspec behavior
body: <p>I try to plot two plots vertically within one figure using gridspec. The upper one is supposed to be twice as high as the lower one (i.e. the ratio is 2:1 with 3 equal vertical parts) and they have to share the x-axis scale. I have the following minimal example, which produces the correct 3-part plot, but it does not span the upper subplot twice as high as the lower one. The first plot is at the top third, the second is in the bottom third, and the middle is emptyWhere is the error?</p>
  
  <pre><code>import matplotlib.gridspec as gridspec
  x = y = [1,2,3]
  gs = gridspec.GridSpec(3, 1)
  ax1 = plt.subplot(gs[0:1, 0])
  ax1.plot(x, y)
  ax2 = plt.subplot(gs[2, 0], sharex=ax1)
  ax2.plot(x,y)
  plt.show()
  </code></pre>