title: writing data frame to pdf table
body: <p>I have a data frame which I would like to write it to a pdf file in organized fashion. </p>
  
  <p>For example, my df looks like this:</p>
  
  <pre><code>Date    County    Trade
  1/1/2012  USA     5
  1/1/2012  Japan   4
  1/2/2012  USA     10
  1/3/2012  Germany 15
  </code></pre>
  
  <p>I would like to output to be group by Date, place a space or line break after each group;</p>
  
  <p>I have this piece of code but this prints out everything to the pdf file without grouping:</p>
  
  <pre><code>library(gridExtra)
  pdf("trade.pdf", height=11, width=8.5)
  grid.table(df)
  dev.off()
  </code></pre>
  
  <p>Any ideas how can best present this data set in a pdf file with grouping on Date? I like to use grid.Extra. Anybody knows how to put a title to grid.Extra?</p>