rand('seed',0); randn('seed',0);
u=rpiid(1024,'exp'); n=25;
y=filter([1,–2], [1,–1.5,0.8], u);
for k=–n:n,
cmat(:,k+n+1)=cumest(y,3,n,128,0,'biased',k);
end
subplot(121), mesh(–n:n,–n:n, cmat)
subplot(122), contour(–n:n,–n:n,cmat,8)