% program ch16ex4.m

clc;close;hold off;echo on % illustrates use of the POLYID software
%
% first load the data
load ch15ex3.mat
% now fit a model
% note this command will lead to an interactive session with user input required
%
[hm,hh,hl,K,theta,tau]=polyid(y1,u1,t1);
close all;

% hm contains the DFIR model
% now compute the step response
u=ones(1,60);
t=0:.1:5.9;
% convolve u with hm to get the step response
ystep=conv(u,hm*.1);
% only the first 60 points are useful
ystep=ystep(1:60);
plot (t,ystep);
% compare with true step response
hold on;
sys=tf(1,[1 1]);sysd=c2d(sys,.1);
[y,t]=step(sysd);
plot(t,y);