How do I create and store data into a new row after every loop?

For example:

I am trying to update the old variable matrix but I am getting an error

f = [1 2 3 4];
a = [1 2 3 4 5 6];
old = 0;
for i = 1:length(a)
    new = f.*a(i);
    old(:,i) = new;
end

I want an old matrix with these values

{1 2 3 4;2 4 6 8;3 6 9 12;4 8 12 16;5 10 15 20; 6 12 18 24}

thank you

Answer 1

[Walter Roberson]

To deliberately grow the old matrix, either initialize

   old = zeros(length(f),0);

or else do not initialize old at all. With what you are doing now, you are initializing old as having only one row, but then trying to write multiple rows to it.

More efficient would be to initialize the entire matrix

old = zeros(length(f), length(a));

This would not grow the matrix as you went: it would start it out as the proper size.

[Jaydeep Dutta]

I see.

I added the code that you mentioned above, but I still receive the following error:

???  In an assignment  A(:,matrix) = B, the number of elements in the subscript of A and the number
of columns in B must be the same.

f = [1 2 3 4];
a = [1 2 3 4 5 6];
old = zeros(length(f),length(a));
for i = 1:length(a)
    new = f.*a(i);
    old(:,i) = new;
end

[Walter Roberson]

To get that error, you must be using a very old MATLAB, such as from 2009.

Try

old(:,i) = new .';

[Jaydeep Dutta]

I should have mentioned earlier..I'm currently using a Matlab v6.1 My apologies and thats a lesson learned Thank you very much :)