title: Subset based on variable column name
body: <p>I'm wondering how to use the <code>subset</code> function if I don't know the name of the column I want to test. The scenario is this: I have a Shiny app where the user can pick a variable on which to filter (subset) the data table. I receive the column name from the webapp as input, and I want to subset based on the value of that column, like so:</p>
  
  <pre><code>subset(myData, THECOLUMN == someValue)
  </code></pre>
  
  <p>Except where both <code>THECOLUMN</code> and <code>someValue</code> are variables.  Is there a syntax for passing the desired column name as a string?</p>
  
  <p>Seems to want a bareword that is the column name, not a variable that holds the column name.</p>