File: score.m

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function [DLIK] = score(T,R,Q,H,P,Y,DT,DYss,DOm,DH,DP,start,mf,kalman_tol,riccati_tol)
% function [DLIK] = score(T,R,Q,H,P,Y,DT,DYss,DOm,DH,DP,start,mf,kalman_tol,riccati_tol)
%
% computes the derivative of the log-likelihood function of
% a state space model (notation as in kalman_filter.m in DYNARE
% thanks to Nikolai Iskrev
%
% NOTE: the derivative matrices (DT,DR ...) are 3-dim. arrays with last
% dimension equal to the number of structural parameters

% Copyright (C) 2009-2011 Dynare Team
%
% This file is part of Dynare.
%
% Dynare is free software: you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% (at your option) any later version.
%
% Dynare is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
% GNU General Public License for more details.
%
% You should have received a copy of the GNU General Public License
% along with Dynare.  If not, see <http://www.gnu.org/licen

    k = size(DT,3);                                 % number of structural parameters
    smpl = size(Y,2);                               % Sample size.
    mm   = size(T,2);                               % Number of state variables.
    a    = zeros(mm,1);                             % State vector.
    Om   = R*Q*transpose(R);                        % Variance of R times the vector of structural innovations.
    t    = 0;                                       % Initialization of the time index.
    oldK = 0;
    notsteady   = 1;                                % Steady state flag.
    F_singular  = 1;

    DLIK  = zeros(k,1);                             % Initialization of the score.
    Da    = zeros(mm,k);                            % State vector.
    Dv    = zeros(length(mf),k);                    % observation vector.
    
%     for ii = 1:k
%         DOm = DR(:,:,ii)*Q*transpose(R) + R*DQ(:,:,ii)*transpose(R) + R*Q*transpose(DR(:,:,ii)); 
%     end
    
    while notsteady & t<smpl
        t  = t+1;
        v  = Y(:,t)-a(mf);
        F  = P(mf,mf) + H;
        if rcond(F) < kalman_tol
            if ~all(abs(F(:))<kalman_tol)
                return
            else
                a = T*a;
                P = T*P*transpose(T)+Om;
            end
        else
            F_singular = 0;
            iF     = inv(F);
            K      = P(:,mf)*iF;

            [DK,DF,DP1] = computeDKalman(T,DT,DOm,P,DP,DH,mf,iF,K);
            for ii = 1:k
                Dv(:,ii)   = -Da(mf,ii)-DYss(mf,ii);
                Da(:,ii)   = DT(:,:,ii)*(a+K*v) + T*(Da(:,ii)+DK(:,:,ii)*v + K*Dv(:,ii));
                if t>=start
                   DLIK(ii,1)  = DLIK(ii,1) + trace( iF*DF(:,:,ii) ) + 2*Dv(:,ii)'*iF*v - v'*(iF*DF(:,:,ii)*iF)*v;
                end
            end
            a      = T*(a+K*v);                   
            P      = T*(P-K*P(mf,:))*transpose(T)+Om;
            DP     = DP1;
        end
        notsteady = max(max(abs(K-oldK))) > riccati_tol;
        oldK = K;
    end

    if F_singular
        error('The variance of the forecast error remains singular until the end of the sample')
    end

    for ii = 1:k
        tmp0(:,:,ii) = iF*DF(:,:,ii)*iF;
    end
    
    if t < smpl
        t0 = t+1;
        while t < smpl
            t = t+1;
            v = Y(:,t)-a(mf);
            for ii = 1:k
                Dv(:,ii)   = -Da(mf,ii)-DYss(mf,ii);
                Da(:,ii)   = DT(:,:,ii)*(a+K*v) + T*(Da(:,ii)+DK(:,:,ii)*v + K*Dv(:,ii));
                if t>=start
                   DLIK(ii,1)  = DLIK(ii,1) + trace( iF*DF(:,:,ii) ) + 2*Dv(:,ii)'*iF*v - v'*(iF*DF(:,:,ii)*iF)*v;
                end
            end
            a = T*(a+K*v);
        end
        for ii = 1:k
%             DLIK(ii,1)  = DLIK(ii,1) + (smpl-t0+1)*trace( iF*DF(:,:,ii) );
        end
        
    end    
    
    DLIK = DLIK/2;
    
% end of main function    
    
function [DK,DF,DP1] = computeDKalman(T,DT,DOm,P,DP,DH,mf,iF,K)

            k      = size(DT,3);
            tmp    = P-K*P(mf,:);

for ii = 1:k
    DF(:,:,ii)  = DP(mf,mf,ii) + DH(:,:,ii); 
    DiF(:,:,ii) = -iF*DF(:,:,ii)*iF;
    DK(:,:,ii)  = DP(:,mf,ii)*iF + P(:,mf)*DiF(:,:,ii);
    Dtmp        = DP(:,:,ii) - DK(:,:,ii)*P(mf,:) - K*DP(mf,:,ii);
    DP1(:,:,ii) = DT(:,:,ii)*tmp*T' + T*Dtmp*T' + T*tmp*DT(:,:,ii)' + DOm(:,:,ii);
end

% end of computeDKalman