i've 2 numpy 2d arrays (say & b, sometime size equal or sometime not equal). need compare first column of both arrays , find index of elements occur in both arrays.
the below shown code gave me solution whenever both arrays have different size , elements of not present in b.
c=np.squeeze(a[np.array(np.where(np.in1d(a[:,0],b[:,1]))).t],axis=none)
but incorrect whenever elements of present in b.
can suggest solution ?
if , b following:
a=np.random.randint(0,5,(10,8)) b=np.random.randint(3,7,(10,8)) >>> array([[4, 4, 2, 1, 4, 3, 1, 2], [1, 1, 1, 2, 0, 3, 0, 4], [4, 3, 1, 1, 2, 1, 1, 3], [3, 4, 3, 0, 3, 4, 2, 0], [4, 1, 3, 0, 1, 4, 1, 2], [1, 1, 1, 2, 2, 2, 0, 2], [4, 3, 4, 2, 3, 2, 3, 2], [4, 1, 4, 0, 3, 1, 2, 3], [3, 2, 3, 2, 4, 4, 4, 2], [0, 1, 4, 0, 2, 2, 1, 4]]) >>> b array([[4, 3, 5, 6, 4, 6, 3, 5], [6, 3, 4, 4, 4, 6, 5, 4], [5, 4, 5, 5, 5, 6, 3, 3], [3, 5, 6, 5, 5, 5, 3, 6], [5, 6, 5, 3, 5, 5, 5, 3], [3, 3, 5, 3, 5, 6, 6, 3], [6, 6, 6, 4, 6, 3, 4, 6], [4, 4, 3, 5, 6, 6, 3, 3], [5, 3, 4, 5, 3, 5, 5, 6], [4, 3, 3, 6, 6, 4, 3, 4]]) you use intersect1d find values in both
np.intersect1d(a,b) array([3, 4]) and argwhere find indices of values in, example, column 0 of a:
[np.argwhere(x==a[:,0]) x in np.intersect1d(a,b)] returns
[array([[3], [8]]), array([[0], [2], [4], [6], [7]])] 
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