title: Regular Expressions in R - exclude keyword
body: <p>There are two variables in my data set with similar names: "JE.Description" and "Field.Description". How can I target the column index of the "JE.Description" column, so as to exclude the word "Field" from the RegExp search? In other words, I would like to modify the command below to only returns the column index of "JE.Description": </p>
  
  <p>The data set is frequently updated and sometimes the "JE.Description" string is shown just as "Description". That is why I am seeking a solution to explicitly excluded the keyword "Field".</p>
  
  <pre><code>r1 &lt;- c(1:5)
  r2 &lt;- c(1:5)
  df &lt;- data.frame(r1,r2)
  names(df)[1] &lt;- "JE.Description"
  names(df)[2] &lt;- "Field.Description"
  
  y &lt;- grep("!^Field^Description",perl = TRUE, colnames(df))
  RETURNS: integer[0]
  </code></pre>
  
  <p>Thanks,</p>