title: Isolate Duplicates Records within qualitative groups R
body: <p>I want to know if it is possible to isolate duplicate records based from a date value but within groups. So essentially, I want extract records where for a given Title, ID, and category where the date values are the same? </p>
  
  <p>Example:</p>
  
  <pre><code>Title   Title_ID   Category     Date
  Title1    2728     Category 1   2013-08-09
  Title1    2728     Category 2   2013-10-18
  Title1    2728     Category 3   2013-11-05
  Title1    2728     Category 4   2013-11-05
  </code></pre>
  
  <p>Desired Output:</p>
  
  <pre><code>Title   Title_ID   Category     Date
  Title1    2728     Category 3   2013-11-05
  Title1    2728     Category 4   2013-11-05
  </code></pre>
  
  <p>Is there a way to accomplish this within R's nifty packages? </p>
  
  <p>Thanks.</p>