title: Group data frame by pattern in R
body: <p>I have R data frame with hundreds of rows as </p>
  
  <pre><code>word        Freq
  seed         4
  seeds        3
  contract     2
  contracting  2
  river        1
  </code></pre>
  
  <p>I would like to group the data by patterns, say seed + seeds ... that looks like</p>
  
  <pre><code>word     Freq
  seed      7
  contract  4
  river     1
  </code></pre>