How do you do an inner product with ruby NArray?

Question

I'm looking for something like the inner method in numpy.

I have a 4 dimensional array called 'labels' and a one dimensional array (a vector) called 'discounts'. In numpy I can do numpy.inner(labels, discounts) and this will do the inner product between discounts and each row of the last dimension of labels returning a 3 dimensional array. I can not figure out how to do the same thing with NArray in ruby.

Answer 1

$ irb -rnarray
irb(main):001:0> a=NArray.float(3,2,2).indgen
=> NArray.float(3,2,2):
[ [ [ 0.0, 1.0, 2.0 ],
    [ 3.0, 4.0, 5.0 ] ],
  [ [ 6.0, 7.0, 8.0 ],
    [ 9.0, 10.0, 11.0 ] ] ]
irb(main):002:0> b=NArray[1..3]
=> NArray.int(3):
[ 1, 2, 3 ]
irb(main):003:0> a*b
=> NArray.float(3,2,2):
[ [ [ 0.0, 2.0, 6.0 ],
    [ 3.0, 8.0, 15.0 ] ],
  [ [ 6.0, 14.0, 24.0 ],
    [ 9.0, 20.0, 33.0 ] ] ]
irb(main):004:0> (a*b).sum(0)
=> NArray.float(2,2):
[ [ 8.0, 26.0 ],
  [ 44.0, 62.0 ] ]
irb(main):005:0> a.mul_add(b,0)
=> NArray.float(2,2):
[ [ 8.0, 26.0 ],
  [ 44.0, 62.0 ] ]