title: Split value from a data.frame and create additional row to store its component
body: <p>In R, I have a data frame called <strong>df</strong> such as the following:</p>
  
  <p><strong>A</strong> &nbsp;&nbsp;&nbsp;&nbsp; <strong>B</strong> &nbsp;&nbsp;&nbsp;&nbsp; <strong>C</strong> &nbsp;&nbsp;&nbsp;&nbsp; <strong>D</strong> <br>
  a1&nbsp;&nbsp;&nbsp;&nbsp;b1&nbsp;&nbsp;&nbsp;&nbsp;c1&nbsp;&nbsp;&nbsp;&nbsp; 2.5 <br>
  a2&nbsp;&nbsp;&nbsp;&nbsp;b2&nbsp;&nbsp;&nbsp;&nbsp;c2&nbsp;&nbsp;&nbsp;&nbsp; 3.5
  <br>
  a3&nbsp;&nbsp;&nbsp;&nbsp;b3&nbsp;&nbsp;&nbsp;&nbsp;c3&nbsp;&nbsp;&nbsp;&nbsp; 5 - 7 <br>
  a4&nbsp;&nbsp;&nbsp;&nbsp;b4&nbsp;&nbsp;&nbsp;&nbsp;c4&nbsp;&nbsp;&nbsp;&nbsp; 2.5   </p>
  
  <p><br>
  I want to split the value of the third row and <strong>D</strong> column by the dash and create another row for the second value retaining the other values for that row.</p>
  
  <p>So I want this:</p>
  
  <p><strong>A</strong> &nbsp;&nbsp;&nbsp;&nbsp; <strong>B</strong> &nbsp;&nbsp;&nbsp;&nbsp; <strong>C</strong> &nbsp;&nbsp;&nbsp;&nbsp; <strong>D</strong> <br>
  a1&nbsp;&nbsp;&nbsp;&nbsp;b1&nbsp;&nbsp;&nbsp;&nbsp;c1&nbsp;&nbsp;&nbsp;&nbsp; 2.5 <br>
  a2&nbsp;&nbsp;&nbsp;&nbsp;b2&nbsp;&nbsp;&nbsp;&nbsp;c2&nbsp;&nbsp;&nbsp;&nbsp; 3.5
  <br>
  a3&nbsp;&nbsp;&nbsp;&nbsp;b3&nbsp;&nbsp;&nbsp;&nbsp;c3&nbsp;&nbsp;&nbsp;&nbsp; 5 
  <br>
  a3&nbsp;&nbsp;&nbsp;&nbsp;b3&nbsp;&nbsp;&nbsp;&nbsp;c3&nbsp;&nbsp;&nbsp;&nbsp; 7<br>
  a4&nbsp;&nbsp;&nbsp;&nbsp;b4&nbsp;&nbsp;&nbsp;&nbsp;c4&nbsp;&nbsp;&nbsp;&nbsp; 2.5</p>
  
  <p>Any idea how this can be achieved?</p>
  
  <p>Ideally, I would also want to create an extra column to specify whether the value I split is either a minimum or maximum. </p>
  
  <p>So this:   </p>
  
  <p><strong>A</strong> &nbsp;&nbsp;&nbsp;&nbsp; <strong>B</strong> &nbsp;&nbsp;&nbsp;&nbsp; <strong>C</strong>  &nbsp;&nbsp;&nbsp;&nbsp; <strong>D</strong> &nbsp;&nbsp;&nbsp;&nbsp; <strong>E</strong> <br>
  a1&nbsp;&nbsp;&nbsp;&nbsp;b1&nbsp;&nbsp;&nbsp;&nbsp;c1&nbsp;&nbsp;&nbsp;&nbsp; 2.5 <br>
  a2&nbsp;&nbsp;&nbsp;&nbsp;b2&nbsp;&nbsp;&nbsp;&nbsp;c2&nbsp;&nbsp;&nbsp;&nbsp; 3.5
  <br>
  a3&nbsp;&nbsp;&nbsp;&nbsp;b3&nbsp;&nbsp;&nbsp;&nbsp;c3&nbsp;&nbsp;&nbsp;&nbsp; 5 &nbsp;&nbsp;&nbsp;&nbsp; min
  <br>
  a3&nbsp;&nbsp;&nbsp;&nbsp;b3&nbsp;&nbsp;&nbsp;&nbsp;c3&nbsp;&nbsp;&nbsp;&nbsp; 7      &nbsp;&nbsp;&nbsp;&nbsp; max
  <br>
  a4&nbsp;&nbsp;&nbsp;&nbsp;b4&nbsp;&nbsp;&nbsp;&nbsp;c4&nbsp;&nbsp;&nbsp;&nbsp; 2.5</p>
  
  <p>Thanks.</p>