如何改动预测往后十年的数据

Question

a=[9.696 9.521 9.497 9.593 9.564 9.821 10.017 9.892...
9.728 9.925 10.082 9.829];
%a=a';a=a:);a=a';
Ri=tiedrank(a)
n=length(a)
i=1:n
Qs=1-6/(n*(n^2-1))*sum((i-Ri).^2)
T=Qs*sqrt(n-2)/sqrt(1-Qs^2)
t_0=tinv(0.975,n-2)
b=diff(a)
m=ar(b,4,'ls')
bhat=predict(m,b')
bhat(end+1)=forecast(m,b',1)
ahat=[a(1),a+bhat']
detla=abs((ahat(1:end-1)-a)./a)