title: Frequency count of two column in R
body: <p>I have two columns in data frame</p>
  
  <pre><code>2010  1
  2010  1
  2010  2
  2010  2
  2010  3
  2011  1
  2011  2
  </code></pre>
  
  <p>I want to count frequency of both columns and get the result in this format</p>
  
  <pre><code>  y    m Freq
   2010  1 2
   2010  2 2
   2010  3 1
   2011  1 1
   2011  2 1 
  </code></pre>