title: Changing text in a data frame
body: <p>I am working with a data frame in which I need to edit the entries in one particular column to allow for easy sorting. The data frame looks like this when imported:</p>
  
  <pre><code>     Assay    Genotype Description Sample   Operator
  1    CCT6-18  C    A.Conservative  1_062911 Automatic   
  2    CCT6-24  C       E.User Call  1_062911   charles
  3    CCT6-25  A    A.Conservative  1_062911 Automatic
  </code></pre>
  
  <p>I need to change the assay column from CCT6-18 to CCT6-018. This "assay" appears multiple times within the data frame and I'd like to change all of the entries at once. Ive tried the gsub function but it returns data in a format that I am unfamiliar with. I'd like to get the data back in a data frame.</p>
  
  <p>Help!</p>