jac.m

这是在网上下的一个东东

%
% Computes forward model derivatives for the EM-38 problem.
%
function J=jac(sigma)
%
% Number of layers.
%
M=11;
%
% Layer thicknesses.
%
D=0.2*ones(10,1);
%
% Operating frequency.
%
f=14600;
OMEGA=2*pi*f;
%
% Distance between coils.
%
R=1.0;
%
% Conductivity of the air above the top layer.
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SIGMA0=0;
%
% Magnetic permeabilities.
%
MU0=pi*4e-7;
MU=MU0*ones(11,1);
%
% Scaling factor Delta.
%
DELTA=sqrt(2/(sigma(1)*MU0*OMEGA));
%
% Heights of measurements.
%
heights=[0.0; 0.1; 0.2; 0.3; 0.4; 0.5; 0.75; 1.0; 1.50];
%
% Now, do the predictions.
%
pred=[];
pred=zeros(length(heights),2);
for i=1:length(heights)
  H=heights(i);
  [predv,predh]=predict(R,DELTA,H,M,MU,MU0,sigma,SIGMA0,D,OMEGA);
  pred(i,:)=[predv predh];
end
%
% Stack up the predictions (vertical over horizontal)
%
f=[pred(:,1); pred(:,2)];
%
% Now, loop through the model parameters, computing derivatives.
%
J=zeros(length(f),M);
I=eye(M);
h=1.0e-8;
for i=1:M
  J(:,i)=(fun(sigma+h*I(:,i))-fun(sigma))/h;
end