Sum of numpy array based on other array

Question

I have two arrays:

array1 =    [[3,7,2],
             [1,4,5],
             [9,8,7]]

array2 =    [[0,1,0],
             [1,0,0],
             [1,0,1]]

I like to get numpy.sum(array1), but only where array2==0

So in the end I like to have a value of 22 (3+2+4+5+8).

score 2 · Accepted Answer · 2014-01-13 22:15:25Z

2

array1 = numpy.array([[3,7,2],
                      [1,4,5],
                      [9,8,7]])

array2 = numpy.array([[0,1,0],
                      [1,0,0],
                      [1,0,1]])

result = numpy.sum(array1[array2==0])
print(result)

Output: 22

You can index numpy arrays with other numpy arrays. Many operators, like ==, can be applied as element-wise operations to numpy arrays.

edited Jan 13, 2014 at 22:15

answered Jan 13, 2014 at 22:08

user3072164

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