How do I count the occurrence of a certain item in an ndarray?

Question

How do I count the number of 0s and 1s in the following array?

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

y.count(0) gives:

numpy.ndarray object has no attribute count

In this case, it is also possible to simply use numpy.count_nonzero. — Mong H. Ng
– Mong H. Ng, Commented Mar 31, 2019 at 17:50

Ishan Tomar · Accepted Answer · 2017-04-26 10:37:05Z

-1

Numpy has a module for this. Just a small hack. Put your input array as bins.

numpy.histogram(y, bins=y)

The output are 2 arrays. One with the values itself, other with the corresponding frequencies.

answered Apr 26, 2017 at 10:37

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2 Comments

isn't 'bins' supposed to be a number?

Yes @johnktejik you're right. This answer does not work.

Suraj Rao · Accepted Answer · 2019-08-19 09:48:14Z

-5

using numpy.count $ a = [0, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 1] $ np.count(a, 1)

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answered Aug 19, 2019 at 9:45

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What's with the dollar signs here?

No such function