If possible, I wouldn't do the inner product manually, I'd use dot, i.e.

 dot([1, 2, 3], [4, 5, 6])

I've noticed that you don't actually have vectors there though, instead you have 1x3 matrices (rows), so if thats really what you have you'd have to vec them first, which is a bit unpleasant:

dot(vec([1 2 3]), vec([4 5 6]))

Alternatively, one could do

 sum([1 2 3].*[4 5 6])

which doesn't care about the dimensions.