title: Is It Possible to Alias data.frame names in R
body: <p>When working with some data standards, it would be simpler to have multiple ways to look at the columns of a data.frame.  As one specific example, when working with SDTM data for clinical trials, each data type (like labs or vital signs) has a column for time point named "LBTPT" for labs and "VSTPT" for vital signs.  When loading the data, ideally, I'd like to be able to refer to that column as either "LBTPT" or "TPT".</p>
  
  <p>Specifically, I'd like to find a way to make something like the following work:</p>
  
  <pre><code>d &lt;- data.frame(LBTPT=1:3)
  d &lt;- alias_column(d, TPT="LBTPT")
  d$TPT == d$LBTPT
  </code></pre>
  
  <p>But, I'd like for the data to only be stored once-- it is just an alias not a copy.</p>
  
  <p>And, for bonus points, it would work in a "do what I mean" way when interacting with functions like <code>merge</code>, <code>names&lt;-</code>, <code>bind_rows</code>, etc.</p>