Problem in surface fitting: Input parameters are not the same as output parameters

Hi everyone,

I am trying to carry out surface fitting of a custom function.

    % These are the inputs for my surface:
                            [X,Y] = meshgrid(1:50,1:50);
                            sigma_value = 2;
                            sigma_value2 = 2; 
                            mu_value = 4 ;
                            angle_wall = pi*1/2 ;                   
                            yCoord_WheretheSimCentres = mu_value ;   
                            xCoord_WheretheSimCentres = 50/2;   
                            AmplitudeofWallSurvFun = (1/20);

    % This is my surface:
       IntensityOfOneRow = (((1/2).*(erfc((Y-yCoord_WheretheSimCentres)./((1.414).*sigma_value))))).*((1./sqrt(2*pi*(sigma_value2).^2)).*(1000).*(AmplitudeofWallSurvFun).*exp((-(-(X - xCoord_WheretheSimCentres).*sin(angle_wall) + (Y - yCoord_WheretheSimCentres).*cos(angle_wall)).^2)./(2.*(sigma_value2.^2))));

I would like to fit the surface using the custom function below, and get the input parameters that I put in, as outputs:

modelFun = fittype( @(p1,p2,p3,p4,X,Y)(((1/2).*(erfc((Y-p1)./((1.414).*p2))))).*((1./sqrt(2*pi*(p3).^2)).*(1000).*(AmplitudeofWallSurvFun).*exp((-(-(X - p1).*sin(p4) + (Y - p1).*cos(p4)).^2)./(2.*(p3.^2)))),'independent',{'X','Y'},'dependent',{'IntensityOfOneRow'} );

      [X,Y] = meshgrid(1:size(IntensityOfOneRow,2),1:size(IntensityOfOneRow,1));
      [XOut, YOut, ZOut] = prepareSurfaceData(X,Y,IntensityOfOneRow) ;
      % This 'prepares' my surface, so that it can be fit.

      Fit_Func = fit([XOut,YOut],ZOut,modelFun) ; 
      % This is the actual fitting step.

disp(Fit_Func)

This procedure, for some reason, does not give my the same input and output parameters.

Could someone please tell me where I am going wrong? I would greatly appreciate it.

Thank you very much,

Aarat

[Samarth Shah]

• Can you tell me about which parameters are you talking about?

Do you mean that when you call prepareSurfaceData, the X, Y, & IntensityOfOneRow are different than XOut, YOut & ZOut respectively?

• Or, do you mean that every time you call the fit function, you get varying coefficients?

You can also contact Technical Support at MathWorks, if you are looking for a quicker resolution.