title: Data frame column naming
body: <p>I am creating a simple data frame like this:</p>
  
  <pre><code>qcCtrl &lt;- data.frame("2D6"="DNS00012345", "3A4"="DNS000013579")
  </code></pre>
  
  <p>My understanding is that the column names should be "2D6" and "3A4", but they are actually "X2D6" and "X3A4". Why are the X's being added and how do I make that stop?</p>