title: r assign characters to a column according to values
body: <p>I have many data frames similar to this:  </p>
  
  <pre><code>  count value
  1   0    7
  2   1   230
  3   2    5
  </code></pre>
  
  <p>I want to add a column to assign colors according to the "value" column. The biggest one should be red, the second one should be blue, the smallest one should be green.</p>
  
  <pre><code>  count value color
  1   0    7    blue
  2   1   230   red
  3   2    5    green
  </code></pre>
  
  <p>Is there an easy way to do it in R? Thanks!</p>