Python: Use array as conditions for another array

Question

Is it possible to simple use an array like:

import numpy as np
a = np.array([1,76,120,158,199]

as an condition array for another array?

I have for example an array like:

b=np.array([0,1,2,3,4,5,76,77,78,79,120,121,122,158,159,199,200,201])

All numbers of array b that are also in array a should get the number 1 for example:

return:

c=np.array([0,1,2,3,4,5,1,77,78,79,1,121,122,1,159,1,200,201])

So is there a fast numpy version to do this. Because the actual array is a huge 3d array with many numbers, which of course could be flattened.

jpp · Accepted Answer · 2018-09-03 17:07:41Z

2

Using numpy.in1d and Boolean indexing:

b[np.in1d(b, a)] = 1

print(b)

array([  0,   1,   2,   3,   4,   5,   1,  77,  78,  79,   1, 121, 122,
         1, 159,   1, 200, 201])

answered Sep 3, 2018 at 17:07

jpp

166k37 gold badges301 silver badges362 bronze badges

Sign up to request clarification or add additional context in comments.

1 Answer 1