title: Plotting a 3D surface plot with contour map overlay, using R
body: <p>I have a 3-tuple data set (X,Y,Z points) that I want to plot using R.</p>
  
  <p>I want to create a surface plot from the data, and superimpose a contour map on the surface plot, so as to create the impression of the contour map being the "shadow" or projection from the surface plot. The contour map is to appear below the surface plot.</p>
  
  <p>My data set looks somewhat like this:</p>
  
  <pre><code>Axis  |  Data Type
  -------------------
  X     |  Date value
  Y     |  Float value
  Z     |  Float value
  </code></pre>
  
  <p>How can I achieve this?</p>