title: Using columns as factors for plotting in R
body: <p>I have a data frame that looks like this:</p>
  
  <pre><code>&gt; head(DOData)
      Date        Site1 Site2  Site3   Site4  Site5  Months
  1   1/1/2012    1.07  3.32   11.35   6.26   5.39   January
  2   1/2/2012    1.24  3.08   10.69   6.57   6.59   January
  3   1/3/2012    1.94  2.69   11.86   6.23   6.23   January
  4   1/4/2012    0.81  3.50   11.47   4.67   5.94   January
  5   1/5/2012    1.41  3.11   10.38   7.44   5.40   January
  6   1/6/2012    2.73  3.28   11.11   6.15   6.22   January
  .
  .
  .
  361 12/26/2012  3.54  3.86   12.67   5.44   6.03   December
  362 12/27/2012  2.05  3.42   10.27   6.05   7.10   December
  363 12/28/2012  3.59  2.96   11.10   6.71   5.68   December
  364 12/29/2012  1.81  3.57   11.20   7.20   7.71   December
  365 12/30/2012  4.03  2.00   11.07   7.15   5.93   December
  366 12/31/2012  1.93  2.03   11.90   6.06   8.46   December
  </code></pre>
  
  <p>i.e. a year's worth of data for 5 sites, with one row per day.</p>
  
  <p>I'd like to create some ggplot2 <code>boxplot</code>'s of data for individual months, using the five sites as factors. I suppose I could put all my data into a single column and then add a new column for the site name, but then I'd still need to somehow select the individual months. I wonder, do I really need to reorganize my data, or is there some way to use the columns as factors?
  Thanks for your help!</p>