Inconsistency in the fitted curve and the plot of obtained fitting parameters

I am trying to fit an equation to a model and I need to call a function "kkrebook2" in my fit type funtion (For "kkrebook2", the inputs are two vectors and its output is a vector). I have attached the way I call "kkrebook2" in my fit type function. When I run my fit code I see the obtained fitted curve (red figure) is different from the plot of the fit type function by using the obtained fitting parameters (yellow figure) which doesn't make sense. This is what I see:

This is the snippet of my fit type function code where I call "kkrebook2" function.

function p = SCR(nu,numGaussians,a,center,sigma)

for i = 1:length(nu)

for k = 1 : numGaussians

if k==1

b = Start;

else

b = Start + (center * (k-1));

end

thisGaussian(i) = a.*exp(-((nu(i)-b).^2)/(2.*(sigma.^2)));

% Add into accumulator array:

gaussEqn1(i) = gaussEqn1(i) + thisGaussian(i);

z(i)= gaussEqn1(i);

end

end

Rn = kkrebook2(nu,z,0);

for i = 1:length(nu)

hi2(i) = (4*pi*n.*nu(i)*L)/c;

hi1(i)=(Rn(i));

f(i)=(-r1+r2*exp(-(z(i))).*exp(-1i*hi1(i)).*exp(-1i*hi2(i)));

g(i)=(1-r1*r2*exp(-(z(i))).*exp(-1i*hi1(i)).*exp(-1i*hi2(i)));

h(i)= f(i)./g(i);

m(i)= abs(h(i));

p(i)= (m(i).^2);

end

end

I have also attached "kkrebook2" function that I call in my code.

Could you please let me know where is the problem? I think it should be in the way I am calling "kkrebook2" but I cannot capture it.

Thanks in advance!

[Voss]

What inputs do you call SCR with?

Can you share the entire definition of the function SCR? Several variables are undefined in the snippet posted so far.

Can you also share the plotting code used to generate the figure?

[Mathieu NOE]

hello

i am not really answering the question, but the poor's man solution (without the curve fiiting toolbox) based on fminsearch does not show any "bizarre" output

clear
load('42nsC.mat')
nu = freq;
p = REF;

Startpoint = 3.778651249339824e+14;
Endpoint = 3.778653249339824e+14;

% Initial conditions
% numGaussians = 9;
% center = (Endpoint - Startpoint)/numGaussians;
% sigma = center/10;
% d0 = 0.05;
% a = 0.23;

numGaussians = 9;
center = 24.1E6;
sigma = 3.4E6;
d0 = 0.04;
a = 0.8;

% curve fit using fminsearch
f = @(a,center,sigma,d0,nu) SCR(nu,numGaussians,a,center,sigma,d0);
obj_fun = @(params) norm(f(params(1), params(2), params(3), params(4),nu)-p);
options = optimset('MaxIter',100);
sol = fminsearch(obj_fun, [a,center,sigma,d0],options);
a_sol = sol(1);
center_sol = sol(2);
sigma_sol = sol(3);
d0_sol = sol(4);

y_fit = f(a_sol, center_sol,sigma_sol, d0_sol, nu); % same output as line below
Sol1= SCR(nu,numGaussians,a_sol,center_sol,sigma_sol,d0_sol); % p = SCR(nu,numGaussians,a,center,sigma,d0)


figure(1)
clf
hold on
plot(nu, p)
plot(nu,Sol1) % This plots the solution above. 
plot(nu,y_fit,'k.') % This plots the solution as well (fit). 
hold off


set(gca,'XTick',Startpoint:1E8:Endpoint)
set(gca,'XTickLabel',-2.87:0.1:-2.67)
xlim([Startpoint Endpoint+15E6])

xlabel('Frequency Offset (GHz)','FontSize', 20)

[Shaily_T]

@Mathieu NOE Thank you so much for your response! I appreciate that.

[Mathieu NOE]

My pleasure !