how to apply Functions on numpy arrays using pandas groupby function

Question

I\'m very new to pandas so I hope this will have an easy answer (and I also appreciate all pointers to even the setup of the dataframe)

So let\'s say I have the foll

Answer 1

For me it works:

D.groupby('gp').apply(lambda x: x.vector.mean().mean())

I'm taking the mean twice, since you want the mean group value for the mean of the vector (don't you?).

Out[98]: 
gp
0     9.0
1     8.5
2     9.5
dtype: float64

If you want the mean vector, just take the mean once.