make a new variable from existing data in pandas dataframe

Question

I need some help with forming a new variable in a dataframe I have a very large dataset were i want to make a new variable from existing data in another column. Here is an example.

I wwant to create a new column with the values a and c in A and name them ac, and the b and d and name them bd Final result should look like. Kind of grouping them from A and give the group a new name in a new column.

>>> df
   A  B   C
0  a  1  ac
1  b  2  bd
2  c  3  ac
3  a  5  ac
4  d  6  bd

/Jonas

a or c should result in ac in C column...that is a and c should be set as beloning to a group called ac.. — jonas
– jonas, Commented Jun 29, 2013 at 14:25

Jeff · Accepted Answer · 2013-06-29 15:06:54Z

1

In [4]: mapper = dict(a = 'ac', b = 'bd', c = 'ac', d = 'bd')

In [5]: df['C'] = [ mapper[x] for x in df['A'] ]

In [6]: df
Out[6]: 
   A  B   C
0  a  1  ac
1  b  2  bd
2  c  3  ac
3  a  5  ac
4  d  6  bd

edited Jun 29, 2013 at 15:06

answered Jun 29, 2013 at 15:01

Jeff

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