Get amount of unique elements in numpy

Question

I have an array
arr = np.array([[1,1,2], [1,2,3]]).
I want to get amount of unique element for each row and count mean
I can do this np.array([len(np.unique(row)) for row in arr]).mean().
But seems, that it's a slow way. Is there another faster approach?

Answer 1

You can use the following:

import numpy as np

arr = np.array([[1, 1, 2], [1, 2, 3]])


mean = np.apply_along_axis(lambda row: len(set(row)), axis=1, arr=arr).mean()

>> mean = 2.5