title: Adding titles to xtable
body: <p>I'm not sure if this is an R question or a Sweave question. I"m looking at students' marks from 2 time points in a simple table (Grade 3 and Grade 6). I've created the table and it prints, however I want to add labels so people know which mark is from which Grade. </p>
  
  <p>My Sweave code is:</p>
  
  <pre><code>&lt;&lt;MakeData,results='asis'&gt;&gt;=
  library(xtable)
  Grade3 &lt;- c("A","B","B","A","B","C","C","D","A","B","C","C","C","D","B","B","D","C","C","D")
  Grade6 &lt;- c("A","A","A","B","B","B","B","B","C","C","A","C","C","C","D","D","D","D","D","D")
  Cohort &lt;- table(Grade3,Grade6)
  print(xtable(Cohort))
  @
  </code></pre>
  
  <p>I get a nice table with counts, however both rows and columns have the same notation. How do I add a label to make it clearer?</p>