Selecting rows from two nump.nd arrays and inserting 0 for missing match
I have two nd.numpy arrays named 'a' and 'b', I want to select only certain rows from 'b' array based on comparison with 'a' and insert 0 for rows if no match is found. I did the first part. eg,
a = np.array([[1,5,9],
[2,6,10],
[5,14,10]])
b = np.array([[ 1,0,9],
[2,6,10],
[4,6,10]])
Output
[[ 1 0 9]
[ 2 6 10]]
expected output
[[ 1 0 9]
[ 2 6 10]
[ 0 0 0]]
code:
import numpy as np
wanted= a[:,[0]]
y=b[np.logical_or.reduce([b[:,0] == x for x in wanted])]
print y
In the above example from array "a" on line "3" we don't have value "5" in array "b" so when comparing "a" with "b" if no match is found I want to insert '0' into the third string so that the dimensions of the two arrays are the same.
If you want any element b[:, 0]
that is not in a[:, 0]
to be zero, you can do the following:
>>> b[~np.in1d(b[:, 0], a[:, 0]), :] = 0
>>> b
array([[ 1, 0, 9],
[ 2, 6, 10],
[ 0, 0, 0]])
If you want any element b[:, 0]
that is not on the matching line a
to be zero:
>>> b[~np.any(b[:, 0][:,None]==a, axis=1), :] = 0
>>> b
array([[ 1, 0, 9],
[ 2, 6, 10],
[ 0, 0, 0]])