title: How to plot aggregated by date pandas dataframe
body: <p>I have this dataframe </p>
  
  <pre><code>df=pd.DataFrame([["2017-01-14",1],
      ["2017-01-14",30],
      ["2017-01-16",216],
      ["2017-02-17",23],
      ["2017-02-17",2],
      ["2017-03-19",745],
      ["2017-03-19",32],
      ["2017-03-20",11],
      ["2017-03-20",222],
      ["2017-03-21",4]],columns=["date","payout_value"])
  </code></pre>
  
  <p>To aggregate <code>payout_value</code> by date I use: </p>
  
  <pre><code>df_daily=df.groupby('date').agg(['sum'])
  
  payout_value
  sum
  date    
  2017-01-14  31
  2017-01-16  216
  2017-02-17  25
  2017-03-19  777
  2017-03-20  233
  2017-03-21  4
  </code></pre>
  
  <p>How do I plot (bar chart) dates on x-axis and aggregated payout sum on y axis? </p>
  
  <p>I tried using <code>df.plot(x='date', y='payout_value',kind="bar")</code> approach, but there is no 'date' column in <code>df_daily</code> dataframe, <code>print(list(df_daily))</code> gives <code>[('payout_value', 'sum')]</code></p>