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function [g, badg] = numgrad(fcn,x,varargin)
% function [g badg] = numgrad(fcn,xvarargin)
%
% Copyright (C) 1997-2012 Tao Zha
%
% This 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.
%
% It 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.
%
% If you did not received a copy of the GNU General Public License
% with this software, see <http://www.gnu.org/licenses/>.
%
%
delta = 1e-6; % works for a general case
%delta = 1e-2; % bigger step -- works for a flat peak
%delta=1e-04;
n=length(x);
tvec=delta*eye(n);
g=zeros(n,1);
%--------------------old way to deal with variable # of P's--------------
%tailstr = ')';
%stailstr = [];
%for i=nargin-2:-1:1
% tailstr=[ ',P' num2str(i) tailstr];
% stailstr=[' P' num2str(i) stailstr];
%end
%f0 = eval([fcn '(x' tailstr]); % Is there a way not to do this?
%---------------------------------------------------------------^yes
f0 = eval([fcn '(x,varargin{:})']);
% disp(' first fcn in numgrad.m ------------------')
%home
% disp('numgrad.m is working. ----') % Jiinil on 9/5/95
% sizex=size(x),sizetvec=size(tvec),x, % Jinill on 9/6/95
badg=0;
for i=1:n
scale=1; % originally 1
% i,tveci=tvec(:,i)% ,plus=x+scale*tvec(:,i) % Jinill Kim on 9/6/95
if size(x,1)>size(x,2)
tvecv=tvec(i,:);
else
tvecv=tvec(:,i);
end
g0 = (eval([fcn '(x+scale*tvecv'', varargin{:})']) - f0) ...
/(scale*delta);
% disp(' fcn in the i=1:n loop of numgrad.m ------------------')% Jinill 9/6/95
% disp(' and i is') % Jinill
% i % Jinill
% fprintf('Gradient w.r.t. %3d: %10g\n',i,g0) %see below Jinill 9/6/95
% -------------------------- special code to essentially quit here
% absg0=abs(g0) % Jinill on 9/6/95
if abs(g0)< 1e15
g(i)=g0;
% disp('good gradient') % Jinill Kim
else
disp('bad gradient ------------------------') % Jinill Kim
% fprintf('Gradient w.r.t. %3d: %10g\n',i,g0) %see above
g(i)=0;
badg=1;
% return
% can return here to save time if the gradient will never be
% used when badg returns as true.
end
end
%-------------------------------------------------------------
% if g0 > 0
% sided=2;
% g1 = -(eval([fcn '(x-scale*tvec(:,i)''' tailstr]) - f0) ...
% /(scale*delta);
% if g1<0
% scale = scale/10;
% else
% break
% end
% else
% sided=1;
% break
% end
% end
% if sided==1
% g(i)=g0;
% else
% if (g0<1e20)
% if (g1>-1e20)
% g(i)=(g0+g1)/2;
% else
% g(i)=0;
% badg=1;
% disp( ['Banging against wall, parameter ' int2str(i)] );
% end
% else
% if g1>-1e20
% if g1<0
% g(i)=0;
% badg=1;
% disp( ['Banging against wall, parameter ' int2str(i)] );
% else
% g(i)=g1;
% end
% else
% g(i)=0;
% badg=1;
% disp(['Valley around parameter ' int2str(i)])
% end
% end
% end
%end
%save g.dat g x f0
%eval(['save g g x f0 ' stailstr]);
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