title: adding a new column to a data.frame in r
body: <p>I have a data.frame which has three column, here is part of the data: </p>
  
  <pre><code>variable lat lon 
  140      40  120
  120      41  120
  115      42  120
  ...
  </code></pre>
  
  <p>This is the rainfall data for different stations. I want to add station-ID as the first column to the above data.frame which is an 1*n array where "n" is the total number of stations. </p>