title: filled contour plot in R
body: <p>I am trying to generate a filled contour plot in R.  My data labels x and y are length 20 vectors, and my z matrix is 20 by 20.  The following is my code, with the filled.contour command copied directly from the r help(filled.contour) file, just with extraneous parameters removed:</p>
  
  <pre><code>x &lt;- seq(1,5)
  y &lt;- seq(1,5)
  cells &lt;- c(1,4,9,16,25,1,4,9,16,25,1,4,9,16,25,1,4,9,16,25,1,4,9,16,25)
  z &lt;- matrix(cells,nrow=5,ncol=5,byrow=TRUE)
  filled.contour(x,y,z,nlevels = 20,col = cm.colors(19))
  </code></pre>