title: Split data.frame row into multiple rows based on commas
body: <p>I am attempting to split a row in a <code>data.frame</code> based on the character sequence ", ". Here's an example:</p>
  
  <pre><code>mydat &lt;- data.frame(v1 = c("name, name2", "name3", "name4, name5"),
                  v2 = c("1, 2", "3", "4, 5"), 
                  v3 = c(1, 2, 3))
  </code></pre>
  
  <p>What I would like to end up with is a <code>data.frame</code> like so:</p>
  
  <pre><code> v1   v2   v3
  name  1    1
  name2  2   1
  name3  3   2
  name4  4   2
  name5  5   3
  </code></pre>
  
  <p>Any suggestions? </p>