How to name structured variable with number that correspond to number of itteration?

How do I name structured variable with number that correspond to itteration in a loop? For example

for l=1:5
  for i=...
    for j=...
S.l{i,j}=...
    end
  end
end

I want to have structured variable S with files 1,2,3,4,5 and inside each file to have cell. thanks!!

Answer 1

[Azzi Abdelmalek]

You can not use a number as a field, try this

for l=1:5
  for i=1:3
      for j=1:4
          S.(sprintf('f%d',l)){i,j}=rand
      end
  end
end