Vectorization of matrices multiplication

Hi,

i have some trouble finding out how to vectorize the following loop:

for k = 1:PointsLength
h(k,1) = transpose(PointsA(:,k) - PointsB(:,k))*normals(:,k);
end

The first thing that comes into my mind is doing this:

all the matrices have 3 x n dimensions and i want h to be 1 x n vector

k = 1:PointsLength
h(:) = transpose(PointsA(:,k) - PointsB(:,k))*normals(:,k);

but its obviously it's not the same thing since im trying to achieve row column multiplication only in pairs ( just k_th row times k_th column, without k_th row times other columns), and thus gives error cause he expects h to be n x n.

Any ideas? Thank you in advance.

[madhan ravi]

Probably you want to use .* (element-wise multiplication) ?

[Eugenio Grabovic]

k = 1:PointsLength
h(:) = transpose(PointsA(:,k) - PointsB(:,k)).*normals(:,k);

gives error cause he wants matrices to have the same dimensions (no transpose),

but by doing that i would only achieve (i_th,j_th) element multiplication only, with a 3 x n h matrix as a result (not what i was looking for).

Answer 1

[Jan]

h = dot(PointsA - PointsB, normals).'

or

h = sum((PointsA - PointsB) .* normals, 1).'

[Eugenio Grabovic]

Oh wow, i feel so stupid... thank you very much !