Problem in defining the fit type function for curve fitting tool

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Shaily_T 2022-5-24

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https://ww2.mathworks.cn/matlabcentral/answers/1725750-problem-in-defining-the-fit-type-function-for-curve-fitting-tool

评论： Shaily_T 2022-5-26

I have defined a custom function for use in curve fitting toolbox. In my defined function, I need to call another function "kkrebook2" and its inputs are vectors. But for defining a fit type function we have a for loop of our "nu" value and everything is defined in that for loop which means the input for "kkrebook2" will be elements of vector of "nu". So, it doesn't work when I try to fit because it is getting elements instead of vectors.

But I do want to pass a vector of "nu" to "kkrebook2" in my fit type function. Could you please let me know how can I write my fit type function such that I can call "kkrebook2" in my fit type function properly?

This is related part of my code for the defined fit type function for curve fitting and the "kkrebook2" function.

Thank you in advance!

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

for i = 1:length(nu)

for k = 1 : numGaussians

if k==1

b = Start;

else

b = Start+(24E6 * (k-1));

end

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

% Add into accumulator array:

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

d(i)= gaussEqn1(i);

end

Imag(i)=(-log(d(i))*c)./(nu(i));

Real(i)=kkrebook2(nu(i),Imag(i),0);

f(i)=(-r1+r2*exp(-(d(i)).*exp(-1i*Real(i)));

g(i)=(1-r1*r2*exp(-(d(i))).*exp(-1i*Real(i)));

p(i)= abs(f(i)./g(i));

end

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Matt J 2022-5-24

There is no variable called 'x' in the code that you've shown.

Shaily_T 2022-5-24

编辑：Shaily_T 2022-5-24

Yes, you are correct. Thanks for capturing that! By "x" I mean "nu" in my code. I edditted my question.

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回答（1 个）

Matt J 2022-5-24

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1725750-problem-in-defining-the-fit-type-function-for-curve-fitting-tool#answer_970855

编辑：Matt J 2022-5-24

在 MATLAB Online 中打开

fittype( @(nu,numGaussians,a,sigma)  SCR(nu,numGaussians,a,sigma),'independent','nu')

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Matt J 2022-5-26

编辑：Matt J 2022-5-26

Here is what I see.

Whether or not this is what you expect is a separate issue from your posted question. Your post is asking how to make fit() invoke your model function and receiving ouput of the proper size. It now appears to be doing that, since no error messages are thrown.

As for why you are not seeing fit results that you expect, there are a number of possible reasons. Your start point could be bad. Or, your model and data may be inconsistent with one another.

Shaily_T 2022-5-26

Yes, that is correct. It is a different issue than what I posted. I posted the question then I was able to make some changes to the fit type function and I see it is working like this which doesn't make sense as the main problem is if I put the obtained fitting parameters in the fit type function I don't see the same result as the fitted curve. I will post another question for it.

Thanks for your time and consideration!

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