title: How to combine two rows in R?
body: <p>I would like to combine/sum two rows based on rownames to make one row in R. The best route might be to create a new row and sum the two rows together. </p>
  
  <p>Example df:</p>
  
  <pre><code>A  1  3  4  6  
  B  3  2  7  9
  C  6  8  1  2 
  D  3  2  8  9
  </code></pre>
  
  <p>Where A,B,C,D are rownames, I want to combine/sum two rows (A &amp; C) into one to get:</p>
  
  <pre><code>A+C  7  11  5  8  
  B    3  2   7  9
  D    3  2   8  9
  </code></pre>
  
  <p>Thank you.</p>