For this DataFrame:
values ii
0 3.0 4
1 0.0 1
2 3.0 8
3 2.0 5
4 2.0 1
5 3.0 5
6 2.0 4
7 1.0 8
8 0.0 5
9 1.0 1
This line returns the error "Must produce aggregated values"
bii2=df.groupby(['ii'])['values'].agg(pd.Series.mode)
While this line works
bii3=df.groupby('ii')['values'].agg(lambda x: pd.Series.mode(x)[0])
Could you explain why is that?
Problem is mode return sometimes 2 or more values, check solution with GroupBy.apply:
bii2=df.groupby(['ii'])['values'].apply(pd.Series.mode)
print (bii2)
ii
1 0 0.0
1 1.0
2 2.0
4 0 2.0
1 3.0
5 0 0.0
1 2.0
2 3.0
8 0 1.0
1 3.0
Name: values, dtype: float64
And pandas agg need scalar in output, so return error. So if select first value it working nice
bii3=df.groupby('ii')['values'].agg(lambda x: pd.Series.mode(x).iat[0])
print (bii3)
ii
1 0.0
4 2.0
5 0.0
8 1.0
Name: values, dtype: float64