How to get the index of np.maximum?

Qimin Chen 0
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I know np.maximum computes the element-wise maximum, e.g.

>>> b = np.array([3, 6, 1])
>>> c = np.array([4, 2, 9])
>>> np.maximum(b, c)
array([4, 6, 9])

But is there any way to get the index as well? like in the above example, I also want something like this where each tuple denote (which array, index), it could be tuple or dictionary or something else. And also it would be great if it could work on 3d array, like the input two arrays are 3d arrays.

array([(1, 0), (0, 1), (1, 2)])
numpy python
1 Answers

You could stack the two 1d-arrays to get a 2d-array and use argmax:

arr = np.vstack((b, c))
indices = np.argmax(arr, axis=0)

This will give you a list of integers, not tuples, but as you know that you compare per column, the last elements of each tuple are unnecessary anyway. They are just ascending integers starting at 0. If you really need them, though, you could just add

indices = list(zip(indices, range(len(b)))
BernieD0
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