title: grouping by day of the week pandas
body: <pre><code>  I have a dataframe,df 
  
          Index       eventName Count   pct
       2017-08-09       ABC     24     95.00%
       2017-08-09       CDE    140     98.50%
       2017-08-10       DEF    200     50.00%
       2017-08-11       CDE    150     99.30%
       2017-08-11       CDE    150     99.30%
       2017-08-16       DEF    200     50.00%
       2017-08-17       DEF    200     50.00%
  </code></pre>
  
  <p>I want to group by daily weekly occurrence by counting the values in the column pct. for example, we now have:</p>
  
  <pre><code> 2017-08-09 has 2 values in pct column  and  2017-08-16 has 1 value in pct, then we have Monday:3 
    2017-08-10  has 1 value and 2017-08-17 has 1 value,then we have Tuesday:2 and so on
  </code></pre>
  
  <p>then the resulting dataframe should look like this:</p>
  
  <pre><code>    Index        Count   
   Monday            3
   Tuesday           2
   Wednesday         2
  </code></pre>
  
  <p>I have tried <code>df2=df.groupby(pd.Grouper(freq='D')).size().sort_values(ascending=False)</code> 
  but its not grouping by day of the week and not transforming to the date index to words</p>