This should be rather straightforward and easy to understand. If not, ask.
A = [10,8,6;1,4,5]
B = [3,4,7;8,9,10]
fid = fopen('delete_me.txt', 'wt');
% Print out the line for A
[rows, columns] = size(A);
fprintf(fid, 'A');
for col = 1 : columns
for row = 1 : rows
fprintf(fid, ',%d,%d,%d', row, col, A(row, col));
end
end
% Now for the B matrix.
[rows, columns] = size(B);
fprintf(fid, '\nB');
for col = 1 : columns
for row = 1 : rows
fprintf(fid, ',%d,%d,%d', row, col, B(row, col));
end
end
fclose(fid);
% In the file, there should be this:
% A,1,1,10,1,2,8,1,3,6,2,1,1,2,2,4,2,3,5
% B,1,1,3,1,2,4,1,3,7,2,1,8,2,2,9,2,3,10
