CODEWITHSUNDEEP
pythonarraysnumpyindexing
Jonathan
Jonathan

Reputation: 303

python numpy array from index array

I have a 3d array a = np.arange(108).reshape(6, 6, 3). I want to grab certain indices of the array, as defined by i = np.array([[0, 1], [1, 3], [2, 1]]) such that the result is [[3, 4, 5], [27, 28, 29], [39, 40, 41]]. I need an efficient way to do this, as my actual arrays are significantly larger.

Upvotes: 1

Views: 42

Answers (1)

akuiper
akuiper

Reputation: 215117

Extract the first and second dimension indices from i, then use advanced indexing:

a[i[:,0], i[:,1], :]   # or a[i[:,0], i[:,1]]

#array([[ 3,  4,  5],
#       [27, 28, 29],
#       [39, 40, 41]])

Upvotes: 2

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