title: Combine two data frames with the same column names
body: <p>I have two data.frame with this format (this is small part of the data sets):</p>
  
  <p>data.frame 1</p>
  
  <pre><code>ID  precip  lat lon
  1   45  115 -122.5
  2   42.5    130 -122.5
  3   40  155 -122.5
  4   37.5    140 -122.5
  </code></pre>
  
  <p>data.frame  2           </p>
  
  <pre><code>    precip  lat lon
  1   108.61  115 -122.5
  2   85.83   130 -122.5
  3   81.01   155 -122.5
  4   NA  140 -122.5
  </code></pre>
  
  <p>I want to add data.frame2 to the end of data.frame1 so at the end I have something like this:</p>
  
  <pre><code>ID  precip  lat lon
  1   45  115 -122.5
  2   42.5    130 -122.5
  3   40  155 -122.5
  4   37.5    140 -122.5
  5   108.61  115 -122.5
  6   85.83   130 -122.5
  7   81.01   155 -122.5
  8   NA  140 -122.5
  </code></pre>