title: R heatmap on imported matlab table
body: <p>I would like to plot a heatmap on a table imported from MATLAB. The table has explicited rownames and colnames and I have loaded it into R with <code>read.table</code>, and I can run <code>summary(i)</code> and get the numeric summaries for each column:</p>
  
  <pre><code>i = read.table("file.txt",header=TRUE)
  </code></pre>
  
  <p>But when I try to run <code>heatmap</code>, it complains the converted matrix is not numeric, both with and without <code>rownames.force=TRUE</code>:</p>
  
  <pre><code>is.matrix(as.matrix(i,rownames.force=TRUE))
  [1] TRUE
  
  heatmap(as.matrix(i,rownames.force=TRUE))
   Error in heatmap(as.matrix(i, rownames.force = TRUE)) : 
     'x' must be a numeric matrix
  </code></pre>
  
  <p>I think the problem is that <code>as.matrix</code> tries to convert the non-numeric rowname (or colname, I am not sure anymore :-(): </p>
  
  <pre><code>as.matrix(i)[1]
  [1] "cluster-594-walk-0161"
  </code></pre>
  
  <p>Any ideas?</p>