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:

In [2]: df = pd.DataFrame({'company': ['ford', 'chevy', 'ford', 'ford', 'ford', 'toyota'],
                     'model': ['mustang', 'camaro', 'fiesta', 'focus', 'taurus', 'camry'],
                     'rating': ['A', 'B', 'C', 'A', 'B', 'B'],
                     'type': ['coupe', 'coupe', 'sedan', 'sedan', 'sedan', 'sedan']})

In [3]: df.groupby('rating').count()['model'] / len(df)
Out[3]:
rating
A    0.333333
B    0.500000
C    0.166667
Name: model, dtype: float64

In [4]: (df.groupby(['rating', 'type']).count() / df.groupby('rating').count())['model']
Out[4]:
rating  type
A       coupe    0.500000
        sedan    0.500000
B       coupe    0.333333
        sedan    0.666667
C       sedan    1.000000
Name: model, dtype: float64