How to match pairs of values contained in two numpy arrays

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I have two sets of coordinates and want to find out which coordinates of the coo set are identical to any coordinate in the targets set. I want to know the indices in the coo set which means I'd like to get a list of indices or of bools.

import numpy as np  coo = np.array([[1,2],[1,6],[5,3],[3,6]]) # coordinates targets = np.array([[5,3],[1,6]]) # coordinates of targets  print(np.isin(coo,targets))  [[ True False]  [ True  True]  [ True  True]  [ True  True]] 

The desired result would be one of the following two:

[False True True False] # bool list [1,2] # list of concerning indices 

My problem is, that ...

  • np.isin has no axis-attribute so that I could use axis=1.
  • even applying logical and to each row of the output would return True for the last element, which is wrong.

I am aware of loops and conditions but I am sure Python is equipped with ways for a more elegant solution.

 


Here's one way taking advantage of broadcasting:

(coo[:,None] == targets).all(2).any(1) # array([False,  True,  True, False]) 

Details

Check for every row in coo whether or not it matches another in target by direct comparisson having added a first axis to coo so it becomes broadcastable against targets:

(coo[:,None] == targets)  array([[[False, False],         [ True, False]],         [[False, False],         [ True,  True]],         [[ True,  True],         [False, False]],         [[False, False],         [False,  True]]]) 

Then check which ndarrays along the second axis have all values to True:

(coo[:,None] == targets).all(2)  array([[False, False],        [False,  True],        [ True, False],        [False, False]]) 

And finally use any to check which rows have at least one True.

Comment

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