find numpy rows that are the same

Question

I have a numpy array

How can I find which of them are the same and how many times appear in the matrix? thanks dummy example:

A=np.array([[0, 1, 0, 1],[0, 0, 0, 0],[0, 1, 1, 1],[0, 0, 0, 0]])

What have you tried so far?

Matt
– Matt

2021-12-29 14:41:41 +00:00
Commented Dec 29, 2021 at 14:41 — Matt
– Matt, Commented Dec 29, 2021 at 14:41

mozway · Accepted Answer · 2021-12-28 08:12:50Z

1

You can use numpy.unique with axis=0 and return_counts=True:

np.unique(A, axis=0, return_counts=True)

Output:

(array([[0, 0, 0, 0],
        [0, 1, 0, 1],
        [0, 1, 1, 1]]),
 array([2, 1, 1]))

answered Dec 28, 2021 at 8:12

mozway

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2 Comments

hilberts_drinking_problem Over a year ago

As an aside, If the number of rows is substantially lager than number of columns, pandas.DataFrame.value_counts can be faster as it avoids sorting rows.

teratoulis Over a year ago

i tried it, it works!! thank you very much!!

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