title: pylab 3d scatter plots with 2d projections of plotted data
body: <p>I am trying to create a simple 3D scatter plot but I want to also show a 2D projection of this data on the same figure. 
  This would allow to show a correlation between two of those 3 variables that might be hard to see in a 3D plot.</p>
  
  <p>I remember seeing this somewhere before but was not able to find it again.</p>
  
  <p>Here is some toy example:</p>
  
  <pre><code>x= np.random.random(100)
  y= np.random.random(100)
  z= sin(x**2+y**2)
  
  fig= figure()
  ax= fig.add_subplot(111, projection= '3d')
  ax.scatter(x,y,z)
  </code></pre>