How to store extracted coefficient values from curve fitting of multiple .txt files in index arrays?

Hi Everyone,

I am doing curve fitting on multiple text files having same input except one. I am using fittype to fit an equation to the experimental data. I have created initial arrays to store extracted coefficients from the curve fitting. After I run code I see the extracted coefficient values of only one .txt file. I am looking for a code that will allow all txt file extracted parameters to be saved in initial arrays. Here is code:

f = fittype( 'C1+C4*(C5^2/(C5^2+(x-C6)^2))+C7*(C5*(x-C6)/(C5^2+(x-C6)^2))+C8*x');
C11=[];
C41=[];
C51=[];
C61=[];
C71=[];
[fit1,gof] = fit(xdata,ydata,f,'StartPoint',[1 -2 20 150 2 2], 'Lower', [-Inf  -Inf -Inf -Inf -Inf -Inf ], 'Upper',[Inf Inf Inf Inf Inf Inf], 'Robust','On');
c1=fit1.C1;
c4=fit1.C4;
c5=fit1.C5;
c6=fit1.C6;
c7=fit1.C7;
c8=fit1.C8;

C=[c4,c5,c6,c7];

Answer 1

[Matt J]

f = fittype( 'C1+C4*(C5^2/(C5^2+(x-C6)^2))+C7*(C5*(x-C6)/(C5^2+(x-C6)^2))+C8*x');

C=nan(5,numFiles);  %pre-allocate

for i=1:numFiles

   xdata=...read
   ydata=...read
    
 [fit1,gof] = fit(xdata,ydata,f,'StartPoint',[1 -2 20 150 2 2], 'Lower', [-Inf  -Inf -Inf -Inf -Inf -Inf ], 'Upper',[Inf Inf Inf Inf Inf Inf], 'Robust','On');

 C(:,i)=coeffvalues(fit1);

end

[Mike]

Thanks a lot. It worked for me. How do I sort which 'i' th coeffvalues refers to which txt file?

[Matt J]

They will be in the same order that they were processed in the loop.

Answer 2

[Sulaymon Eshkabilov]

It can be done something like this way:

Folder = 'C:\Users\...';   % Directory where the files are residing
F_Pat = fullfile(Folder, '*.txt');
FILES = dir(F_Pat);
F_Names={FILES.name};
f = fittype( 'C1+C4*(C5^2/(C5^2+(x-C6)^2))+C7*(C5*(x-C6)/(C5^2+(x-C6)^2))+C8*x');
C11=[];
C41=[];
C51=[];
C61=[];
C71=[];
C81 =[];
for k = 1 :length(F_Names)
    Get_FName = FILES(k).name;
    F_FileName=fullfile(FILES(k).folder, Get_FName);
    D= readmatrix(F_FileName);
xdata=D(:,1);
ydata=D(:,2);
[fit1,gof] = fit(xdata,ydata,f,'StartPoint',[1 -2 20 150 2 2], 'Lower', [-Inf  -Inf -Inf -Inf -Inf -Inf ], 'Upper',[Inf Inf Inf Inf Inf Inf], 'Robust','On');
c1=fit1.C1;
c4=fit1.C4;
c5=fit1.C5;
c6=fit1.C6;
c7=fit1.C7;
c8=fit1.C8;
C=[c4,c5,c6,c7];
C11=[C11, c1];
C41=[C41, c4];
C51=[C51, c5];
C61=[C61, c6];
C71=[C71, c7];
C81=[C81, c8];
end