n=length(un);
start=456;
predict=zeros(n-start,1);
predict2=zeros(n-start,1);
beta=zeros(n-start,2);
for i=1:n-start
    beta(i,:)=[ones(start+i-2,1) un(1:start+i-2,:)]\un(2:start+i-1,:);
    predict(i)=[1 un(start+i-1,:)]*beta(i,:)';
    predict2(i)=un(start+i-1);
end
rmse=sqrt(sum((un(457:n,:)-predict).^2)/(n-start));
rmse2=sqrt(sum((un(457:n,:)-predict2).^2)/(n-start));

x=1:1:n-start;
plot(x,predict,x,predict2,x,un(457:n,:))
legend('AR Forecast','RW Forecast', 'Actual');
title(['Comparing AR and RW Forecasts']);
xlabel('Time')
ylabel('%')