[Numpy-discussion] How to implement a 'pivot table?'
Geoffrey Zhu
zyzhu2000 at gmail.com
Mon Jul 30 11:12:06 EDT 2007
Hi Everyone,
I am wondering what is the best (and fast) way to build a pivot table
aside from the 'brute force way?'
I want to transform an numpy array into a pivot table. For example, if
I have a numpy array like below:
Region Date # of Units
---------- ---------- --------------
East 1/1 10
East 1/1 20
East 1/2 30
West 1/1 40
West 1/2 50
West 1/2 60
I want to transform this into the following table, where f() is a
given aggregate function:
Date
Region 1/1 1/2
----------
East f(10,20) f(30)
West f(40) f(50,60)
I can regroup them into 'sets' and do it the brute force way, but that
is kind of slow to execute. Does anyone know a better way?
Thanks,
Geoffrey
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