Normalize DataFrame by group

Question

Let\'s say that I have some data generated as follows:

N = 20
m = 3
data = np.random.normal(size=(N,m)) + np.random.normal(size=(N,m))**3

and t

Answer 1

In [10]: df.groupby('indx').transform(lambda x: (x - x.mean()) / x.std())

should do it.