Nested for loops - FOR expression comma separated list Error

When I try to run this code:

A = zeros(30000, NV);
counter = 1;
for k = 1:P
    for n = GN(:,k)
        for i = AT{n}
            A(counter, pMap(i,1,1)) = - w(i,k);            
        end
        counter = counter + 1;
    end
end

I am getting this error: "FOR expression comma separated list must have exactly one item".

I am not sure what is going on.

NV is some number like 7000.

GN is a matrix of the form

[1 2 3;
2 3 4;
3 4 5]

AT is a cell array where its entries are arrays of the form:

AT{1} = [1 2 3 4 5 6 7 8 9 10];
AT{2} = [11 12 13 14 15 16 17 18 19 20]; etc...

Any help would be appreciated.

Answer 1

[Matt J]

for n = GN(:,k).'  %<-- note transpose