How do I multiply 3 vectors and obtain a 3D matrix in MATLAB?

Question

What I'm trying to do is obtain results like the snippet below without a loop.

x = [1 2 3 4];
y = [2 3 4];
z=[7 8];

[x'*y]

for k=1:size(z, 2)
z2(:,:,k)=[x'*y]*z(k);
end

z2

Loops may slow down MATLAB, however. How do I approach the task without them?

Answer 1

You can just do this because z is ` vector:

bsxfun(@times, reshape(z, 1, 1, []), [x'*y])

If z was a 2D matrix itself and you wanted to do a matrix multiplication at each level then you would need to use the links I posted in my comment. But because each time you are multiplying by a scalar, you can use @times .

Answer 2

Have a look here . Base on this, you could do as follows:

x = [1 2 3 4];
y = [2 3 4];
z=[7 8];


% replicate [x'*y] into 3D array.
d = repmat([x'*y], [1, 1, numel(z)])

% multiplay by z vector
z2 = bsxfun(@times, d, reshape(z,[1, 1, numel(z)]))