title: R, rowMeans by Column in data.frame
body: <p>I have a csv that I've read in and is now a data.frame within R.  My file name is MyRData007.  My header information goes until row 5 (main column headers are on row 4).  My ID is in column A.  I simply need to create two separate rowMeans for each ID.  The data is in rows 5-147.  For the first mean it's columns 4-15; the second mean it's for columns 6-21.  Ultimately I'll should have a new variable with a mean for each of the 143 rows.  This is what I tried:</p>
  
  <pre><code>&gt; mRNA&lt;-rowMeans(MyRData007)[5:147,(4:15)]
  &gt; Protein&lt;-rowMeans(MyRData007)[5:147,(16:21)]
  </code></pre>
  
  <p>But I get an error?</p>
  
  <pre><code>Error in rowMeans(MyRData007) : 'x' must be numeric
  </code></pre>