title: Prevent automatic conversion of single column to vector
body: <p>I have a data frame like this:<br>
  <code>df = data.frame(a=1:3, b=2:4, c=3:5)</code>  </p>
  
  <p>I am selecting columns from that data frame using something akin to:<br>
  <code>df[, c(T, F, T)]</code></p>
  
  <p>This works fine as long as there are at least two columns to be returned; but, if I do this for example:<br>
  <code>df[, c(T, F, F)]</code>   </p>
  
  <p>... I suddenly only get a vector instead of a data.frame.  </p>
  
  <p>Normally this would be fine (or even desired), but since I need the result to be a data.frame at a later point, this completely messes up my scripts.</p>
  
  <p>Is there a way I can prevent R from doing this automatic conversion to a vector for single-column selections?</p>