title: Breaks in a heatmap
body: <p>I am trying to use breaks in a heatmap:</p>
  
  <pre><code>col_breaks = c(seq(-4,-1.99999,length=100), 
                  seq(-2,1.999999,length=100),
                  seq(2,4,length=100));
   png("../graphs/mRNA_levels.png",
       width = 5*300,
       height = 5*300,
       res = 300,
       pointsize = 8
   );
   heatmap.2(x = t(scale(t(exp.data.breast))),
             main = "chemokine levels in tumour samples",
             trace = "none",
             margins = c(5,5),
             col = my_palette,
             breaks=col_breaks                                       
      );
  </code></pre>
  
  <p>I get this error. </p>
  
  <blockquote>
    <p>Error in image.default(1:nc, 1:nr, x, xlim = 0.5 + c(0, nc), ylim = 0.5 +  : 
      must have one more break than colour</p>
  </blockquote>
  
  <p>Could anybody explain what the problem is in a simple way?</p>