Simple cross-tabulation in pandas

Question

I stumbled across pandas and it looks ideal for simple calculations that I\'d like to do. I have a SAS background and was thinking it\'d replace proc freq -- it looks like it\'l

Answer 1

Assuming that you have a file called 2010.csv with contents

category,value
AB,100.00
AB,200.00
AC,150.00
AD,500.00

Then, using the ability to apply multiple aggregation functions following a groupby, you can say:

import pandas
data_2010 = pandas.read_csv("/path/to/2010.csv")
data_2010.groupby("category").agg([len, sum])

You should get a result that looks something like

          value     
            len  sum
category            
AB            2  300
AC            1  150
AD            1  500

Note that Wes will likely come by to point out that sum is optimized and that you should probably use np.sum.