How to calculate conditional probability of values in dataframe pandas-python?

Question

I want to calculate conditional probabilites of ratings(\'A\',\'B\',\'C\') in ratings column.

    company     model    rating   type
0   ford       mustang          


        

Answer 1

You can use .groupby() and the built-in .div():

rating_probs = df.groupby('rating').size().div(len(df))

rating
A    0.333333
B    0.500000
C    0.166667

and the conditional probs:

df.groupby(['type', 'rating']).size().div(len(df)).div(rating_probs, axis=0, level='rating')

coupe  A         0.500000
       B         0.333333
sedan  A         0.500000
       B         0.666667
       C         1.000000