Documentation of th2poly

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Function Synopsis

[a,b,c,d,f,lam,T]=th2poly(th)

Help text

TH2POLY computes the polynomials associated with a given model.
   [A,B,C,D,F,LAM,T]=TH2POLY(TH)

   TH is the model with format described by (see also) THETA.

   A,B,C,D, and F are returned as the corresponding polynomials
   in the general input-output model. A, C and D are then row
   vectors, while B and F have as many rows as there are inputs.
   LAM is the variance of the noise source.
   T is the sampling interval.
   See also POLY2TH.

Cross-Reference Information

Listing of function th2poly

function [a,b,c,d,f,lam,T]=th2poly(th)

%   L. Ljung 10-1-86, 8-27-94
%   Copyright (c) 1986-98 by The MathWorks, Inc.
%   $Revision: 2.3 $  $Date: 1997/12/02 03:40:02 $

if nargin < 1
   disp('Usage: [A,B,C,D,F,NOISE_VARIANCE] = TH2POLY(TH)')
   return
end

if isthss(th),error('TH2POLY does not work for state-space models and Multivariable ARX-models. Use TH2TF or TH2ARX instead!'),end
T=gett(th);lam=th(1,1);
nu=th(1,3);
nb=[];nc=[];nd=[];nk=[];nf=[];
na=th(1,4);
if nu>0,nb=th(1,5:4+nu);end
nc=th(1,5+nu);,nd=th(1,6+nu);
if nu>0,nf=th(1,7+nu:6+2*nu);,nk=th(1,7+2*nu:6+3*nu);end
Nacum=na;,Nbcum=Nacum+sum(nb);,Nccum=Nbcum+nc;,Ndcum=Nccum+nd;
Nfcum=Ndcum+sum(nf);
a=[1 th(3,1:Nacum)];
c=[1 th(3,Nbcum+1:Nccum)];
d=[1 th(3,Nccum+1:Ndcum)];
if nu==0, b=0;,f=1;,end
b=zeros(nu,max(nb+nk));nf1=max(nf)+1;f=zeros(nu,nf1);
s=1;,s1=1;
for k=1:nu
      if nb(k)>0,
      b(k,nk(k)+1:nk(k)+nb(k))=th(3,na+s:na+s+nb(k)-1);
      end
      if T>0,if nf(k)>0,
      f(k,1:nf(k)+1)=[1 th(3,Ndcum+s1:Ndcum+nf(k)+s1-1)];
      else f(k,1)=1;end
      else, if nf(k)>0
      f(k,nf1-nf(k):nf1)=[1 th(3,Ndcum+s1:Ndcum+nf(k)+s1-1)];
      else f(k,nf1)=1;end
      end
      s=s+nb(k);,s1=s1+nf(k);
end