prodgiv.m

various matlab programs to slove various problems

function Q=prodgiv(c,s,n)
n1=n-1; n2=n-2;
Q=eye(n); Q(n1,n1)=c(n1); Q(n,n)=c(n1);
Q(n1,n)=s(n1); Q(n,n1)=-s(n1);
for k=n2:-1:1, 
   k1=k+1; Q(k,k)=c(k); Q(k1,k)=-s(k);
   q=Q(k1,k1:n); Q(k,k1:n)=s(k)*q; 
   Q(k1,k1:n)=c(k)*q;
end
return