title: Getting more info from Rprof()
body: <p>I've been trying to dig into what the time-hogs are in some R code I've written, so I'm using <code>Rprof</code>.  The output isn't yet very helpful though:</p>
  
  <pre><code>&gt; summaryRprof()
  $by.self
                        self.time self.pct total.time total.pct
  "$&lt;-.data.frame"           2.38     23.2       2.38      23.2
  "FUN"                      2.04     19.9      10.20      99.6
  "[.data.frame"             1.74     17.0       5.54      54.1
  "[.factor"                 1.42     13.9       2.90      28.3
  ...
  </code></pre>
  
  <p>Is there some way to dig deeper and find out which specific invocations of <code>$&lt;-.data.frame</code>, and <code>FUN</code> (which is probably from <code>by()</code>), etc. are actually the culprits?  Or will I need to refactor the code and make smaller functional chunks in order to get more fine-grained results?</p>
  
  <p>The only reason I'm resisting refactoring is that I'd have to pass data structures into the functions, and all the passing is by value, so that seems like a step in the wrong direction.</p>
  
  <p>Thanks.</p>