// 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 [Se,R,T]=sensi(G,Sk,flag)
    // [Se,R,T]=sensi(G,Sk) computes sensitivity functions
    // If flag='o' or no flag:
    // [Se;R;T]= [inv(eye+G*K);K*inv(eye+G*K);G*K*inv(eye+G*K)];
    //
    // flag='i'
    // [Si,Ri,Ti]= [inv(eye+K*G);G*inv(eye+K*G);K*G*inv(eye+K*G)];
    //!

    [LHS,RHS]=argn(0);
    if RHS==2 then flag="o";end
    select flag
    case "o"
        G1=G(1);Sk1=Sk(1);
        ssflag=0;
        if G1(1)=="r" then G=tf2ss(G);ssflag=1;end
        if Sk1(1)=="r" then Sk=tf2ss(Sk);ssflag=ssflag+1;end
        [ny,nu]=size(G);Iu=eye(nu,nu);Iy=eye(ny,ny);
        Ouy=zeros(nu,ny);Oyu=zeros(ny,nu);Ouu=zeros(nu,nu);
        Oyy=zeros(ny,ny);
        W1=[Iy,Oyu,Oyy;
        Ouy,Iu,Ouy;
        -Iy,Oyu,Iy;
        Iy,Oyu,Oyy];
        W2=[Iy,-G;
        Ouy,Iu;
        Iy,Oyu];
        SRT=lft(W1*W2,Sk);
        Se=SRT(1:ny,:);
        R=SRT((ny+1):(ny+nu),:);
        T=SRT((nu+ny+1):(nu+ny+ny),:);
        if ssflag >0 then
            Se=ss2tf(Se);R=ss2tf(R);T=ss2tf(T);
        end
    case "i"
        G1=G(1);Sk1=Sk(1);
        ssflag=0;
        if G1(1)=="r" then G=tf2ss(G);ssflag=1;end
        if Sk1(1)=="r" then Sk=tf2ss(Sk);ssflag=ssflag+1;end
        [ny,nu]=size(G);Iu=eye(nu,nu);Iy=eye(ny,ny);
        Ouy=zeros(nu,ny);Oyu=zeros(ny,nu);Ouu=zeros(nu,nu);
        Oyy=zeros(ny,ny);
        W1=[Iu,-Iu;
        Oyu,Oyu;
        Ouu,Iu;
        Oyu,Oyu];
        W2=[Ouy;Iy;Ouy;Iy];
        W3=[Iu,-Iu];
        P=W1+W2*G*W3;
        SRT=lft(P,Sk);
        Se=SRT(1:nu,:);
        R=SRT((nu+1):(ny+nu),:);
        T=SRT((nu+ny+1):(nu+ny+nu),:);
        if ssflag >0 then
            Se=ss2tf(Se);R=ss2tf(R);T=ss2tf(T);
        end
    end
endfunction