title: Recode catagorical variable as integers in Pandas
body: <p>I've asked this question for R but am now trying to do it in pandas. I'm trying to use pandas to recode a categorical variable to integers. Given:</p>
  
  <pre><code>group
   005j         
   005j         
   0k16         
   0fff       
   0fff
  </code></pre>
  
  <p>I'd like to get a series of increasing integers representing the same grouping:</p>
  
  <pre><code>group   intCode
   005j      1   
   005j      1   
   0k16      2   
   0fff      3 
   0fff      3
  </code></pre>