function id = subjectid(n,periods)

% this program generates random id numbers for n
% subjects

% it creates a (periods x n) matrix of random integers b/w 1 and n
% on a given row, an interger is nerver repeated twice

% written by:
% Guillaume R. Frechette
% frechette.6@osu.edu

rand('state',0)	% ensures the sate (seed) of the generator is
% always the same

id=rand(periods,n);

for i=1:periods
   [s,position]=sort(id(i,:));
   [s,rank]=sort(position);
   id(i,:)=rank;
end