function X=rvperm(N, n, M, seed) 
% rvperm(N, n, M, seed)  Generates a matrix in which each row contains n 
%                        permutations of N, with a total of M rows.  seed is 
%                        the seed for the random number generator. 
if n>N 
   error('n > N') 
end 
range=[1:N]; 
rand('seed', seed); 
X=zeros(M, n); 
for trial=1:M, 
   for pick=1:n, 
      flag=0; 
      while flag==0 
         flag=1; 
         pindex=round(rand*length(range)+0.5); 
         if pindex>length(range) 
            pindex=length(range); 
         end 
         for check=1:pick-1, 
            if X(trial, check)==range(pindex) 
               flag=0; 
            end 
         end 
      end 
      X(trial, pick)=range(pindex); 
   end 
end