Python And Numpy : Subtracting Line By Line A 2-dim Array From A 1-dim Array

In python, I wish to subtract line by line a 2-dim array from a 1-dim array. I know how to do it with a 'for' loop and indexes but I suppose it may be quicker to use numpy function

Solution 1:

The problem is that y-x have the respective shapes (2) (2,5). To do proper broadcasting, you'll need shapes (2,1) (2,5). We can do this with .reshape as long as the number of elements are preserved:

y.reshape(2,1) - x

Gives:

array([[19, 18, 17, 16, 15],
   [ 4,  3,  2,  1,  0]])

Solution 2:

y[:,newaxis] - x 

should work too. The (little) comparative benefit is then you pay attention to the dimensions themselves, instead of the sizes of dimensions.