Custom equation error in fitting toolbox
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Pietro Scapolo
el 10 de Dic. de 2021
Comentada: Pietro Scapolo
el 10 de Dic. de 2021
Hi, I'm trying to fit my data with a specific function trough the fitting tool. The equation that my datas should fit is
, it's the distribution of a laser light interference when it pass trought one fenditure.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/829815/image.png)
By the way the fitting tool cannot fit my data, the error reported is: "NaN computed by model function, fitting cannot continue.
Try using or tightening upper and lower bounds on coefficient". I think the problem is cause by
because when I dont add to the box there's no error.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/829820/image.png)
2 comentarios
Alex Sha
el 10 de Dic. de 2021
Hi, post out your data if possible, it will be convenient for others to try your problem
Respuesta aceptada
Chunru
el 10 de Dic. de 2021
The following function will result in undefined value for sin(x)=0
sin(a*sin(x))/(a*sin(x))
You can change this into sinc function (which take care of 0/0 case):
sinc(a*sin(x)/pi)
% which is equivalent to the first expression and eliminate the problem at
% sin(x)=0.
% doc sinc
3 comentarios
Chunru
el 10 de Dic. de 2021
% The whole function should be
b*(sinc(a*sin(x)/pi)).^2
% the above is part of the function that cause the problem
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