Adding a frequency column to a pandas dataframe

Asked May 15 '18 at 18:10

Active May 15 '18 at 18:13

Viewed 647 times

Suppose I have a dataframe with TransID, prop, weeknum

It looks like this

A1234    a    1
B234     a    1
C333     b    1
D444     b    1

How can I add a new column to this dataframe which will be a count of all rows belonging to a {prop, weeknum}. Thus in this example the new column would contan '2' for every row.

asked May 15 '18 at 18:10

Mark Ginsburg

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What are the column headers here? – cs95 May 15 '18 at 18:11
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Looks like you want `df.groupby(['prop', 'weeknum']).transform('count')` – cs95 May 15 '18 at 18:11

Adding a frequency column to a pandas dataframe

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