function z=walsh(n,m)
   i=log(n)/log(2);
   h=0;
   for k=1:i
       p=ones(size(h));
       h1=xor(p,h);
       h=[h h;h h1];
   end
   for t=1:n
       if h(m,t)==1
           h(m,t)=-1;
       else
           h(m,t)=1;
       end    
   end   
   z=h(m,:);