title: R - Group by variable and then assign a unique ID
body: <p>I am interested in de-identifying a sensitive data set with both time-fixed and time-variant values.  I want to (a) group all cases by social security number, (b) assign those cases a unique ID and then (c) remove the social security number.</p>
  
  <p>Here's an example data set:</p>
  
  <pre><code>personal_id    gender  temperature
  111-11-1111      M        99.6
  999-999-999      F        98.2
  111-11-1111      M        97.8
  999-999-999      F        98.3
  888-88-8888      F        99.0
  111-11-1111      M        98.9
  </code></pre>
  
  <p>Any solutions would be very much appreciated.</p>