title: Reshape and merge columes in R
body: <p>So i have a question of transpose data in R.
  I have a set of data looking like the following:</p>
  
  <pre><code> id startdate   enddate
   1  10/15/2008  .
   1  .           .
   1  .           .
   1  .           08/25/2009
   2  12/09/2008  .
   2  .           12/18/2008
  </code></pre>
  
  <p>I want to make the data look like</p>
  
  <pre><code>  id startdate  endend
    1  10/15/2008 08/25/2009
    2  12/09/2008 12/18/2008
  </code></pre>
  
  <p>Does anyone have an idea of how to do it??
  Thank you very very much!!</p>