% example ch19ex5.m
%
% load previously stored data
load ch19ex5_reg_data;
scal=ch19ex5_reg_data;
% extract vectors
load ch19ex5_test_data;
test=ch19ex5_test_data;

time=scal(:,1); x=scal(:,2);y=scal(:,3);
tt=test(:,1);xt=test(:,2);yt=test(:,3);
z=[y x];
idplot(z,[],1);% this program is from identification toolbox
% now fit the data to a first order arx model
% try various time delays
for i=1:10
th1=arx(z,[1 1 i]); % arx is an id_toolbox function that implements 
% the least squares fit for the parameters the results are
% stored in a structure variable called th1
% the parameters are na,nb and nk. 
present(th1); % this prsents the model
pause;
y1sim=idsim(xt,th1);
pe=yt-y1sim;penorm(i)=sqrt(sum(pe .*pe))

% compare step responses of all models
end;
plot(penorm);