title: How to determine num entries per minute in pandas data
body: <p>I am trying to get a breakdown of how many times an entry in the 'f' column is listed per minute.</p>
  
  <pre>
      import pandas as pd
      import datetime as dt
  
      f= ['f0001',
          'f0001',
          'f0001',
          'f0001',
          'f0020',
          'f0008',
          'f0001',
          'f0005',
          'f3203',
          'f0002',
          'f0002',
          'f0001',
          'f0201',
          'f0001',
          'f0439',
          'f0233',
          'f0008',
          'f0003',
          'f0009',
          'f0005']
  
  
      dates = ['20130101100103', '20130101100110',
                 '20130101100125', '20130101100133',
                 '20130101100100', '20130101100200',
                 '20130101100200', '20130101100200',
                 '20130101100200', '20130101100200',
                 '20130101100200', '20130101100300',
                 '20130101100300', '20130101100300',
                 '20130101100300', '20130101100400',
                 '20130101100400', '20130101100400',
                 '20130101100400', '20130101100400']
  
  
      d = {'date':  dates}
      data = pd.DataFrame(d)
      data['user'] = f
  
      data.date = data.date.apply(str)
      data.date = data.date.apply(lambda x: 
      dt.datetime.strptime(x,'%Y%m%d%H%M%S'))
  
      s = data.groupby([data.date.map(lambda t: t.minute)]).count()
  </pre>
  
  <p>But so far all I've got is the below </p>
  
  <pre>
  s
  
      date    user
  date        
  1   5   5
  2   6   6
  3   4   4
  4   5   5
  </pre>