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function [h,err]=time_id(n,u,y)
// Copyright INRIA
[lhs,rhs]=argn(0)
y=y(:)
npt=size(y,'*');
select type(u)
case 1 then
u=u(:)
case 10 then
select part(u,1)
case 'i' then
u=eye(npt,1)
case 's' then
u=ones(npt,1)
else
error(' time_id: waiting for ''i'' or ''s'' ')
end
else
error(' time_id: waiting for ''i'' or ''s'' ')
end
if y(1)==0 then // strictly proper case
m(npt-1,2*n)=0;
for k=1:n,m(k:npt-1,[k k+n])=[-y(1:npt-k) u(1:npt-k)];end
coef=m\y(2:npt);
num=poly(coef(2*n:-1:n+1),'z','c');
den=poly([coef(n:-1:1);1],'z','c');
else
m(npt,2*n+2)=0;
for k=1:n+1,m(k:npt,[k k+n+1])=[-y(1:npt-k+1) u(1:npt-k+1)];end
coef=-m(:,2:$)\m(:,1)
num=poly(coef(2*n+1:-1:n+1),'z','c');
den=poly([coef(n:-1:1);1],'z','c');
end
h=syslin('d',num,den)
if lhs==2 then
err=norm(y-rtitr(num,den,u')',2)
end
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