title: Pandas dataframe groupby plot
body: <p>I have a dataframe which is structured as:</p>
  
  <pre><code>          Date   ticker  adj_close 
  0   2016-11-21     AAPL    111.730     
  1   2016-11-22     AAPL    111.800    
  2   2016-11-23     AAPL    111.230    
  3   2016-11-25     AAPL    111.790     
  4   2016-11-28     AAPL    111.570    
  ...          
  8   2016-11-21      ACN    119.680            
  9   2016-11-22      ACN    119.480              
  10  2016-11-23      ACN    119.820              
  11  2016-11-25      ACN    120.740 
  ...             
  </code></pre>
  
  <p>How can I plot based on the ticker the <code>adj_close</code> versus <code>Date</code>?  </p>