title: Source only part of a file
body: <p>My R workflow is usually such that I have a file open into which I type R commands, and I’d like to execute those commands in a separately opened R shell.</p>
  
  <p>The easiest way of doing this is to say <code>source('the-file.r')</code> inside R. However, this always reloads the whole file which may take considerable time if big amounts of data are processed. It also requires me to specify the filename again.</p>
  
  <p>Ideally, <strong>I’d like to source only a specific line (or lines) from the file</strong> (I’m working on a terminal where copy&amp;paste doesn’t work).</p>
  
  <p><code>source</code> doesn’t seem to offer this functionality. Is there another way of achieving this?</p>