熊猫数据框中分类列的概率

Question

I have a pandas dataframe like this

0 Age color country
1  23  red    Us
2  25  black  UK
3  19  blue   UK
4  10  red    India
5  15  red    UK

What I want to do is to find the probability of each category in 'color' column and have something like this:

0 Age color country  color_pro
1  23  red    Us       0.6 
2  25  black  UK       0.2
3  19  blue   UK       0.2
4  10  red    India    0.6
5  15  red    UK       0.6

What should I do for finding probability in a tuple? like this:

0 color color_pro
1 red    0.6 
2 black  0.2
3 blue   0.2
4 red    0.6
5 red    0.6

I want to have the probability in another tuple:

0 color_pro
1  0.6 
2  0.2
3  0.2
4  0.6
5  0.6

Answer 1

Use groupby and count to get the values, then calculate proportion.

df['color_pro'] = df.groupby('color')['color'].transform('count')
df['color_pro'] = df['color_pro'].map(lambda x : x/len(df))

OR, clubbing both lines together, we can do this as well.

df['color_pro'] = df.groupby('color')['color'].transform(lambda x : x.count()/len(df))