Documentation of th2tf

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Function Synopsis

[num,den]=th2tf(th,iu)

Help text

TH2TF  Transforms from the THETA-format to transfer functions.
   [NUM,DEN] = TH2TF(TH,IU)

   TH: The model, defined in the THETA-format (See also THETA).

   IU: The input number (default 1) to be considered. Noise source
       number ni is counted as input number -ni.
   NUM: The numerator(s) of the transfer function. For a multivariable
        model row k of NUM gives the transfer function from input # IU
        to output # k.
   DEN: The denominator of the transfer function. (Common to all outputs)

   NUM and DEN are given in the standard formats of the Control Systems
   Toolbox (both for continuous and discrete time models)
   See also TH2FF, TH2POLY, TH2SS and TH2ZP.

Cross-Reference Information

Listing of function th2tf

function [num,den]=th2tf(th,iu)

%   L. Ljung 10-2-90
%   Copyright (c) 1986-98 by The MathWorks, Inc.
%   $Revision: 2.3 $  $Date: 1997/12/02 03:44:31 $

if nargin < 1
   disp('Usage: [NUMERATOR(S), DENOMINATOR] = TH2TF(TH)')
   disp('       [NUMERATOR(S), DENOMINATOR] = TH2TF(TH,INPUT_NUMBER)')
   return
end

nu=th(1,3);
if nargin<2,if nu>0,iu=1;else iu=-1;end,end;if iu==0,iu=-1;end
if iu>nu,error('There are not that many inputs in the system'),end
if isthss(th),
        [a,b,c,d,k]=th2ss(th);
        [mc,nc] = size(c);dk=eye(mc);
        den = poly(a);
        if iu>0,b = b(:,iu);d=d(:,iu);
        else b=k(:,-iu);d=dk(:,-iu);end

        num = ones(mc, nc+1);
        for i=1:mc
                num(i,:) = poly(a-b*c(i,:)) + (d(i) - 1) * den;
                nnd(i)=max(find(abs(num(i,:))>eps));
        end

nd=max(find(abs(den)>eps));ord=max([nd nnd]);
den=den(1:ord);num=num(:,1:ord);

return,end
nu=th(1,3);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

[a,b,c,d,f]=th2poly(th);T=th(1,2);
if iu>0,den=conv(a,f(iu,1:nf(iu)+1));else den=conv(a,d);end
if iu>0,num=b(iu,1:nb(iu)+nk(iu));else num=c;end
ld=length(den);ln=length(num);mn=max(ld,ln);
if T>0,den=[den,zeros(1,mn-ld)];num=[num,zeros(1,mn-ln)];
else den=[zeros(1,mn-ld),den];num=[zeros(1,mn-ln),num];end