How to combine two rows in R?
<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>