title: Plotting by the index in pandas
body: <p>I have a data set  that contains the colour of an item, the date and the number of colour picks. I stored it into a Data Frame like this:  </p>
  
  <pre><code>             date    | picks |        
           ------------+-------|
  colour
  orange    2016-01-01 |     6 | 
            2016-01-01 |     4 | 
            2016-01-01 |    16 | 
  black     2016-01-01 |     0 | 
            2016-01-02 |     7 | 
            2016-01-02 |     0 | 
   green    2016-01-02 |     8 | 
            2016-01-02 |     5 | 
            2016-01-03 |     4 | 
  </code></pre>
  
  <hr>
  
  <pre><code>df = pd.DataFrame(
      {'colour': ['orange', 'orange', 'orange', 'black', 'black', 'black', 'green',
                  'green', 'green'], 
       'date': ['2016-01-01', '2016-01-01', '2016-01-01', '2016-01-01', '2016-01-02',
                '2016-01-02', '2016-01-02', '2016-01-02', '2016-01-03'], 
       'picks': [6, 4, 16, 0, 7, 0, 8, 5, 4]})
  df['date'] = pd.to_datetime(df['date'])
  df = df.set_index('colour')
  </code></pre>
  
  <p>I would like to plot subplots (picks vs. date) for each colour i.e. subplot by index. is there a way to do this?</p>
  
  <p>This is what I have tried so far:  </p>
  
  <pre><code>fig, axes=plt.subplot(1,3)
  for subp in axes:
      df.plot(ax=sub,subplot=True)
  </code></pre>
  
  <p>But this is showing an error.
  I also tried this:  </p>
  
  <pre><code>df.plot(ax=[axes[0,0],axes[0,1],axes[0,2],subplot=True)
  </code></pre>
  
  <p>This one works, however I want to know how can I iterate and do this instead of simply giving the parameters.</p>