How to groupby and compute the probability in pandas

Question

I have a dataframe as follows

id1, id2, thumb_up
 1,  1,   1
 1,  2,   -1
 1,  3,   1
 2, 1,   1
 2,  3,  -1
and so on

I want to create the following dataframe

id1, thumb_up_prob
 1, 0.66 ( 2 positive feedback and 1 negative = 2/3)
 2, 0.5 (1 positive and 1 negative feedback = 1/2)

and so on.. so basically i want to groupby id1 and compute the probability. How do i do this in pandas.

Answer 1

• check if df.thumb_up is equal to 1
• groupby df.id1
• since bool is subset of int we cal call mean on it

---

df.thumb_up.eq(1).groupby(df.id1).mean()

Answer 2

With apply function and lambda

# df
df = pd.DataFrame({'id1':[1,1,1,2,2], 'id2':[1,1,3,1,3], 'thumb_up':
[1,-1,1,1,-1]})

# probability
df.groupby('id1').apply(lambda x: x[x>0].count()/len(x)) 

output:

 id1    id2 thumb_up
 id1            
 1  1.0 1.0 0.666667
 2  1.0 1.0 0.500000