title: Merge data sets based on two column values
body: <p>I have looked everywhere and I cannot seem to find a workable solution to this small problem I am having.</p>
  
  <p>I have two large data sets, N=875 and N=922.</p>
  
  <p><code>df.1</code> data set with 875 obs and 27 var
  <code>df.2</code> data set with 922 obs 23 var</p>
  
  <p><code>df.1</code> has columns <code>FIRST</code> and <code>LAST</code> which are the first and last names of the individuals, and 25 other columns.</p>
  
  <p><code>df.2</code> has columns <code>X1</code> and <code>X2</code> which correspond to the first and last names of the individuals, and 21 other columns.</p>
  
  <p>I need to merge <code>df.1</code> with <code>df.2</code> and throw away any observations that are not in both frames.</p>
  
  <p>So I should now have a data frame with less that 875 observations and 48 columns.</p>
  
  <p>Any suggestions?</p>
  
  <p>Thanks</p>