title: heatmap2 : Error in axis(1, at = xv, labels = lv) : no locations are finite
body: <p>I am trying to plot a non symmetrical and non squared matrix using heatmap2.
  But I am getting a message error :</p>
  
  <pre><code>Error in axis(1, at = xv, labels = lv) : no locations are finite
  Calls: heatmap.2 -&gt; axis
  Execution halted
  </code></pre>
  
  <p>In fact, my data are in the matrix are equal to 0, 1 or ? (missing values).
  For example with this matrix : </p>
  
  <pre><code>dat_mat
                     C1  C2
  P17612|KAPCA_HUMAN  ?   0
  P22612|KAPCG_HUMAN  0   1
  P22694|KAPCB_HUMAN  1   0
  P31751|AKT2_HUMAN   0   0 
  </code></pre>
  
  <p>The expected result should be a heatmap with red color for "0", green for "1" and nothing (blank) for "?". Here is the R script I am using : </p>
  
  <pre><code>heatmap.2(dat_mat, 
  Rowv = FALSE, 
  Colv = FALSE, 
  dendrogram = "none",
  scale = "none",
  margins = c(12,24),
  key = TRUE,
  keysize = 1.0,
  col = rainbow(512, start = 1, end = 0.4), 
  density.info="density", 
  denscol = "black",
  xlab="Compounds", 
  ylab="Targets", 
  main="X Activity Profile",
  tracecol = "black")
  </code></pre>