CODEWITHSUNDEEP
pythonpython-3.xpandas
quant
quant

Reputation: 4482

How to get the percentage of occurrence of a value in a column into a new column, in pandas

I have a dataframe that looks like this:

import pandas as pd
foo = pd.DataFrame({'id':[1,1,2,2], 'val':[1,1,1,0]})

I would like to create a new column, which will have the percentage of val == 1 by id

The resulting dataframe should look like this:

foo = pd.DataFrame({'id':[1,1,2,2], 'val':[1,1,1,0], 'percentage':[1,1,0.5,0.5})

Any ideas how I can do that ?

Upvotes: 1

Views: 33

Answers (1)

jezrael
jezrael

Reputation: 862661

If there is only 0,1 values you can use mean with GroupBy.transform for new column:

foo['percentage'] = foo.groupby('id')['val'].transform('mean')
print (foo)
   id  val  percentage
0   1    1         1.0
1   1    1         1.0
2   2    1         0.5
3   2    0         0.5

If any values in val is necessary first compare by Series.eq:

foo['percentage'] = foo['val'].eq(1).groupby(foo['id']).transform('mean')

Upvotes: 1

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