CODEWITHSUNDEEP
matlab
Tyler Ram
Tyler Ram

Reputation: 13

Matlab: Return multiple parameter values from a nlinfit (right now I only go through one index of the loop)

I am trying to pass three cell2mat arrays for I,V,H through this function and plot the result of the parameter from the nlinfit model below. But when the code is run it plots nothing and only stores one value. Any help is appreciated:) 

function [Icp] = Fraunhofer_Function(I,V,H)        

V1 = @(b,I)(b(1).*sign(I).*real(sqrt(I.^2 - (sign(I).*(   (b(2)+b(3)/2)  )).^2)) + b(4));
Vthresx = find(V<=1e-3 & V>=0);
Ithresvec = max(I(Vthresx));

Voffsetx = find(I<=0.1e-3 & I>=-.1e-3);
Voffset = max(V(Voffsetx));

Rn =  (max(V)-min(V))/(max(I)-min(I));

beta1 = [Rn; Ithresvec; -Ithresvec; Voffset]; %Init values  b1=Rn b2 = Icp, b3 = Icm, b4 = Voffset
opts = statset('MaxIter', 500000, 'MaxFunEvals', 100000, 'RobustWgtFun', 'andrews');
B1 = nlinfit(I, V, V1, beta1, opts ); %Fit 
Icp = V1(B1,V);


end



  files = dir('*.xlsx*');
  for k =1:length(files)
  filenames = files(k).name;

  txt = 'I,V,H';
  [num,txt,raw] = xlsread(filenames);

  %Put data into numerical columns
  Idata = num(:,1)'; Vdata = num(:,2)'; Hdata = num(:,3)';        
  [Hu,~,idx] = unique(Hdata);
  Isplit = splitapply(@(x) {x}, [Idata(:)],idx);
  Vsplit = splitapply(@(x) {x}, [Vdata(:)],idx);
  Hsplit = splitapply(@(x) {x}, [Hdata(:)],idx);    

  for l = 1:length(Isplit)

      I = (Isplit{l,1});
      V = (Vsplit{l,1});
      H = (Hsplit{l,1});

     %fit the data to the functional form
      Icp = Fraunhofer_Function(I,V,H);              

  end

end

Example of the I,V,H, data is below:enter image description here

Upvotes: 0

Views: 131

Answers (1)

rinkert
rinkert

Reputation: 6863

Right now you are just setting Icp to the second estimated coefficient. From the Matlab docs nlinfit, the output beta:

beta — Estimated regression coefficients vector

Estimated regression coefficients, returned as a vector. The number of elements in beta equals the number of elements in beta0.

So to use the estimated parameters, you should call your modelfun, with the parameters stored in B1:

Icp = V1(B1,V);
plot(H,Icp);

Upvotes: 0

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