title: Delete duplicate rows in two columns simultaneously
body: <p>I would like to delete duplicate rows based in two collumns, instead just one.</p>
  
  <p>My input <code>df</code>:</p>
  
  <pre><code>RAW.PVAL  GR     allrl  Bak
  0.05      fr     EN1    B12
  0.05      fg     EN1    B11
  0.45      fr     EN2    B10
  0.35      fg     EN2    B066
  </code></pre>
  
  <p>My output:</p>
  
  <pre><code>RAW.PVAL  GR  allrl   Bak
  0.05      fr   EN1    B12
  0.45      fg   EN2    B10
  0.35      fg   EN2    B066
  </code></pre>
  
  <p>I had tried <code>df&lt;- subset(df, !duplicated(allrl, RAW.PVAL))</code>, but I do not work to delete rows with this two columns simultaneously duplicated.</p>
  
  <p>Thank you!</p>