title: Comparing previous row values in Pandas DataFrame
body: <pre><code>import pandas as pd
  data={'col1':[1,3,3,1,2,3,2,2]}
  df=pd.DataFrame(data,columns=['col1'])
  print df
  
  
           col1  
      0     1          
      1     3          
      2     3          
      3     1          
      4     2          
      5     3          
      6     2          
      7     2          
  </code></pre>
  
  <p>I have the following Pandas DataFrame and I want to create another column that compares the previous row of col1 to see if they are equal.  What would be the best way to do this?  It would be like the following DataFrame.  Thanks</p>
  
  <pre><code>    col1  match  
  0     1   False     
  1     3   False     
  2     3   True     
  3     1   False     
  4     2   False     
  5     3   False     
  6     2   False     
  7     2   True     
  </code></pre>