title: Formatting of list into a data.frame in R with some aggregation
body: <p>I am still running around with this, I have a list like this below</p>
  
  <pre><code>     Date sulfate nitrate ID
  289 2001-10-16    0.77   0.156  3
  301 2001-10-28    2.26   0.812  3
  313 2001-11-09    7.22   2.350  3
  319 2001-11-15    4.06   1.100  3
  325 2001-11-21    1.38   1.170  3
  343 2001-12-09    5.22   3.760  3
  </code></pre>
  
  <p>I need to get the count of number of rows in respect to ID Value. My end result should be a data.frame which should look like</p>
  
  <pre><code>##   id value
  ## 1  3  243
  </code></pre>
  
  <p>I prefer not to use a "for" loop to get this done - if nothing else would give that a try</p>