Count the frequency of each element categorical values in python [duplicate]

Question

Is there a simple way to do this in Python?

For example I have:

x = np.array(['a', 'b', 'a', 'b', 'b', 'u'])

Desired outcome:

[2, 3, 2, 3, 3, 1]

You can select an answer even after your question is closed. I'd recommend doing so, since the relatively new arguments to np.unique make the answer more efficient than the accepted one of the duplicate. — Mad Physicist
– Mad Physicist, Commented Oct 20, 2019 at 3:37

Mad Physicist · Accepted Answer · 2019-10-20 02:31:23Z

3

Use np.unique with return_counts and return_inverse enabled:

_, inverse, count = np.unique(x, return_inverse=True, return_count=True)
result = count[inverse]

answered Oct 19, 2019 at 14:29

Mad Physicist

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2 Comments

You missed return_count argument

@tstanisl. Wow. Much appreciated :)