How can I store all outputs from a nested for loop?

I know this might be a common problem, and tried a lot of different answers posted under similar questions. Anyway, here's a basic idea.

a = rand(2,3);
b = rand(2,3);
c = rand(2,3);

for i=1:length(a(:,1))
    for j=1:length(a(1,:))
            z = [a(i,j), b(i,j), c(i,j)]
    end
end

As you can see, I get a 1x3 matrix for z in every iteration, but I want to store them, so I'd have a z as 6x3. I know I haven't preallocated for z here, btw.

Answer 1

[Stephen23]

This is easier using linear indexing:

a = rand(2,3);
b = rand(2,3);
c = rand(2,3);
z = nan(numel(a),3); % preallocate
for k = 1:numel(a)
    z(k,:) = [a(k),b(k),c(k)];
end
display(z)

z = 6×3

0.8970 0.9894 0.0327 0.1664 0.5844 0.5157 0.1946 0.8872 0.6354 0.5858 0.9135 0.5917 0.1652 0.9554 0.0871 0.9033 0.2481 0.6914