title: How to convert time to decimal
body: <p>I have a large data set containing time in hh:mm:ss format and I would like to convert these to a decimal format while ignoring the hours (hh). I have used strptime but this does not seem to convert it. </p>
  
  <p>To be more precise I would like to change <code>00:01:38</code> into <code>1,6333</code> and <code>01:18:30</code> into <code>78,5</code>.</p>
  
  <p>How do I do this in R?</p>