// Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
// Copyright (C) INRIA
//
// This file must be used under the terms of the CeCILL.
// This source file is licensed as described in the file COPYING, which
// you should have received as part of this distribution.  The terms
// are also available at
// http://www.cecill.info/licences/Licence_CeCILL_V2.1-en.txt

function [lt,grad]=iirgroup(p,r,theta,omega,wt,td)
    //    p===> Lp
    //    r=magnitude of poles and zeros of filters
    //theta=phase   "    "   "    "    "
    //omega=frequencies corresponding to filters specs.
    //wt=weighting function for group delay
    //!
    [m,n]=size(td);if m>n,td=td';end;
    [m,n]=size(omega);if m>n,omega=omega';end;
    [m,n]=size(r);if n>m,r=r';m=n;end;
    [m,n]=size(theta);if n>m,theta=theta';m=n;end;
    m=m/2;
    //
    //VARIABLES LOCALES
    unr=ones(r);unom=ones(omega);un=unr(1:m,:).*.unom;
    n1=r.*.unom;n2=unr.*.omega;n3=theta.*.unom;n4=(unr+r.*r).*.unom;
    cw=cos(omega);sw=sin(omega);ct=cos(theta);st=sin(theta);
    c=cw.*.ct;s=sw.*.st;cos1=c+s;cos2=c-s;
    c=sw.*.ct;s=cw.*.st;sin1=c-s;sin2=c+s;
    //
    //FORMES QUADRATIQUES
    k1=n4-2*n1.*cos1;k2=n4-2*n1*cos2;
    //
    //RETARD DE GROUPE
    grp=[];k3=k1(1:m,:);k4=k1(m+1:2*m,:);k5=k2(1:m,:);k6=k2(m+1:2*m,:);
    c1=cos1(1:m,:);c2=cos1(m+1:2*m,:);c3=cos2(1:m,:);c4=cos2(m+1:2*m,:);
    r1=n1(1:m,:);r2=n1(m+1:2*m,:);
    t=(un-r2.*c2)./k4+(un-r2.*c4)./k6-(un-r1.*c1)./k3-(un-r1.*c3)./k5;
    for k=t,grp=[grp sum(k)];end;
    //
    //GRADIENT DU RETARD DE GROUPE
    k1=k1.*k1;k2=k2.*k2;
    grrgrp=(n4.*cos1-2*n1)./k1+(n4.*cos2-2*n1)./k2;
    grrgrp(1:m,:)=-grrgrp(1:m,:);
    n5=n1.*(-n4+2*unr.*.unom);
    grtgrp=(n5.*sin1)./k1-(n5.*sin2)./k2;
    grtgrp(1:m,:)=-grtgrp(1:m,:);
    //
    //CRITERE D'ERREUR EN LE RETARD DE GROUPE ET SON GRADIENT
    t=grp-td;t1=t^(2*p);t1=t1.*wt;lt=sum(t1);
    t1=(t1./t)*2*p;
    grad=[grrgrp*t1' grtgrp*t1'];
endfunction