title: Problems with pheatmap usage
body: <p>I'm trying to play around with <code>pheatmap</code> and getting stuck at the very beginning.</p>
  
  <p>Creating a toy example:</p>
  
  <pre><code>library(pheatmap)
  set.seed(1)
  my.mat &lt;- matrix(rnorm(90), nrow = 30, ncol = 30)
  rownames(my.mat) &lt;- 1:30
  colnames(my.mat) &lt;- 1:30
  col.scale = colorRampPalette(c("red", "blue"), space = "rgb")(10)
  breaks.size = 11
  pheatmap(my.mat, color = col.scale, breaks = breaks.size, border_color = NA, cellwidth = 10, cellheight = 10)
  </code></pre>
  
  <p>Throws this error message:</p>
  
  <pre><code>Error in unit(y, default.units) : 'x' and 'units' must have length &gt; 0
  </code></pre>
  
  <p>And the plot it produces doesn't seem right:</p>
  
  <p>For example, I can't understand why the top right cells are white. i also thought the setting  <code>cellwidth = 10</code> and <code>cellheight = 10</code> means getting square cells and not rectangular. And finally, if anyone knows if it's possible to have the row names and col names apear on the same side of the heat map as the dendograms (i.e., at the tips of the dendogram), that'll be great.
  <img src="https://i.stack.imgur.com/TqHp9.png" alt="enter image description here"></p>