Generating a design matrix with for loops

Hello everyone, I am trying to create a design matrix for simulation puposes using for loops with vectors, but I am struggeling with what to write in the inner most loop. The numbers are arbitrary, to get the hang of it, I need to be able to scale it up for vectors with 100 values or more.

The code looks as follows:

a = (1: 3)';
b = (4: 6)';
c = (7: 9)';

for i = a
    for j = b
        for k = c
            e(i, j k)=...
        end
    end
end

The result should be a matrix with all posibilities of combinations of the 3 vectors and should look like:

e = 1 4 7
    1 4 8
    1 4 9
    1 5 7
    1 5 8
    1 5 9
    1 6 7
    1 6 8
    1 6 9
    2 4 7...

Hope you guys can help, thanks!

Answer 1

[Yongjian Feng]

Something like this?

a = (1: 3);
b = (4: 6);
c = (7: 9);

idx = 1;
for i = a
    for j = b
        for k = c
            e(idx, 1) = i;
            e(idx, 2) = j;
            e(idx, 3) = k;
            idx = idx + 1;
        end
    end
end
e