title: Remove certain rows based on matching
body: <p>I have this data set:</p>
  
  <pre><code>data &lt;- data.frame(trip_id = c("456B", "123A", "123A", "456B", "456B", "123A", "789C", "789C"),
                     comment = c("void", "", "", "", "", "void", "", "void"),
                     paid = c(0, 100, 100, 250, 250, 0, 125, 0))
  
  print(data)
  #trip_id comment paid 
  #   456B    void    0
  #   123A          100
  #   123A          100
  #   456B          250
  #   456B          250
  #   123A    void    0
  #   789C          125
  #   789C    void    0
  </code></pre>
  
  <p>I want to be able to programmatically remove rows with "void" in the <code>comment</code> field, as well as a row for every <code>trip_id</code> that has a corresponding row with a "void" in the <code>comment</code> field. Using the example, the output would look like the following:</p>
  
  <pre><code>print(solution)
  #trip_id comment paid 
  #   123A          100
  #   456B          250
  </code></pre>