title: converting a matrix of lists to a regular matrix
body: <p>Take the following code:</p>
  
  <pre><code>foo &lt;- list()
  foo[[1]] &lt;- list(a=1, b=2)
  foo[[2]] &lt;- list(a=11, b=22)
  foo[[3]] &lt;- list(a=111, b=222)
  result &lt;- do.call(rbind, foo)
  result[,'a']
  </code></pre>
  
  <p>In this case, <code>result[,'a']</code> shows a list.  Is there a more elegant way such that <code>result</code> is a "regular" matrix of vectors?  I imagine there are manual ways of going about this, but I was wondering if there was an obvious step that I was missing.</p>