Custom equation error in fitting toolbox
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Pietro Scapolo
am 10 Dez. 2021
Kommentiert: Pietro Scapolo
am 10 Dez. 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 Kommentare
Alex Sha
am 10 Dez. 2021
Hi, post out your data if possible, it will be convenient for others to try your problem
Akzeptierte Antwort
Chunru
am 10 Dez. 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 Kommentare
Chunru
am 10 Dez. 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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