title: matplotlib 3d surface plots not showing
body: <p>I am trying to make a simple 3D surface plot with matplotlib but the plot does not show at the end; I only get empty 3D axes.</p>
  
  <p>Here is what I did:</p>
  
  <pre><code>from mpl_toolkits.mplot3d import Axes3D
  
  x = np.arange(1, 100, 1)
  y = np.arange(1, 100, 1)
  z = np.arange(1, 100, 1)
  
  fig = figure()
  ax = fig.add_subplot(111, projection='3d')
  ax.plot_surface(x, y, z, rstride=5, cstride=5) 
  show()
  </code></pre>
  
  <p>...and I get this:
  <img src="https://i.stack.imgur.com/AAlx4.png" alt="enter image description here"> </p>
  
  <p>Any suggestions? </p>