Lesson 6

Lets take a look at the groupby function.



In [1]:

    
# Import libraries
import pandas as pd
import sys



In [2]:

    
print 'Python version ' + sys.version
print 'Pandas version: ' + pd.__version__









    



Python version 2.7.5 |Anaconda 2.1.0 (64-bit)| (default, Jul  1 2013, 12:37:52) [MSC v.1500 64 bit (AMD64)]
Pandas version: 0.15.2



In [3]:

    
# Our small data set
d = {'one':[1,1,1,1,1],
     'two':[2,2,2,2,2],
     'letter':['a','a','b','b','c']}

# Create dataframe
df = pd.DataFrame(d)
df



In [4]:

    
# Create group object
one = df.groupby('letter')

# Apply sum function
one.sum()



In [5]:

    
letterone = df.groupby(['letter','one']).sum()
letterone



In [6]:

    
letterone.index









    Out[6]:





MultiIndex(levels=[[u'a', u'b', u'c'], [1]],
           labels=[[0, 1, 2], [0, 0, 0]],
           names=[u'letter', u'one'])

You may want to not have the columns you are grouping by become your index, this can be easily achieved as shown below.



In [7]:

    
letterone = df.groupby(['letter','one'], as_index=False).sum()
letterone



In [8]:

    
letterone.index









    Out[8]:





Int64Index([0, 1, 2], dtype='int64')

Author: David Rojas