title: Replace the values of two dataframe columns based on the values of a column of another data frame
body: <p>I have the 2 dataframes below:</p>
  
  <pre><code>Names&lt;-c("Max","Helen","Bob","Eva")
  Id&lt;-c(1,2,3,4)
  LISTN&lt;-data.frame(Names,Id)
  
  Name1&lt;-c("Max","Bob")
  Name2&lt;-c("Helen","Eva")
  PAIRS&lt;-data.frame(Name1,Name2)
  </code></pre>
  
  <p>I would like to replace the values of the columns <code>Name1</code> and <code>Name2</code> of the <code>PAIRS</code> with the respective <code>Id</code> found in the <code>LISTN</code>. The result should look like:</p>
  
  <pre><code>Name1 Name2
  1     1     2
  2     3     4
  </code></pre>