title: Place legend at specific heatmap.2 column and row in r
body: <p>Is it possible to place a legend at a specific column &amp; row in heatmap.2?</p>
  
  <p>I.e.</p>
  
  <pre><code>&gt; mymatrix = matrix(0,2,2)
  &gt; mymatrix
       [,1] [,2]
  [1,]    0    0
  [2,]    0    0
  
  heatmap.2(mymatrix, col=bluered, Rowv = FALSE, trace="none", Colv = FALSE, main="Legend positioning")
  </code></pre>
  
  <p>I'd like to mark a circle, via legend, at mymatrix[2,2] in the heatmap.2</p>