title: R data frame remove column using grep - columns don't get remove
body: <p>I have following loop: </p>
  
  <pre><code>columns.to.remove &lt;- c('C_', 'WWTest_', 'TotalClick', 'IPA_', 'Sell', 'G_')
  for (i in length(columns.to.remove)) {
  
    final.frame &lt;- final.frame[, -grep(columns.to.remove[i], colnames(final.frame))]
  }
  </code></pre>
  
  <p>But when i look at the data frame by trying to do <code>final.frame$G_</code> its still shows up as all. </p>