How to resolve : increase max function value in fitting using fminsearch?

Question

Somnath Kale 2022-6-16

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1741910-how-to-resolve-increase-max-function-value-in-fitting-using-fminsearch

编辑： Matt J 2022-6-18

采纳的回答： Matt J

data.txt

在 MATLAB Online 中打开

Hi

I was trying to fit my data with fminsearch function with following code:

f = @(a,b,c,x) a - b.*(x).^c;
obj_fun = @(params) norm(f(params(1), params(2), params(3), x) -y);
sol = fminsearch(obj_fun, [1,1,1]);
err = .02*ones(size(x));
errorbar(x,y,err,'horizontal','s',"MarkerFaceColor",[0.8500, 0.3250, 0.0980], ...
    "MarkerSize",4,"CapSize",4,"Color",[0.8500, 0.3250, 0.0980],"LineWidth",1)
hold on
x = linspace(min,max,20);
plot(x,f(sol(1),sol(2),sol(3),x),'-',"Color",[0.8500, 0.3250, 0.0980],"LineWidth",1)
hold off

Its getting the fit, but I think this is not best optimum fit its showing following message:

 Exiting: Maximum number of function evaluations has been exceeded
         - increase MaxFunEvals option.
         Current function value: 2.586758 

it will be realy great if some experties help me here to take care of this. Im attaching data here (data.txt).

Is there any other function which I can use instade of this to fit and better gobal optimazation.

Thank you in advance!

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Matt J 2022-6-16

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1741910-how-to-resolve-increase-max-function-value-in-fitting-using-fminsearch#answer_987060

编辑：Matt J 2022-6-16

在 MATLAB Online 中打开

You could do as the message says and increas MaxFunEvals, but for your model, it would be better to download fminspleas,

https://www.mathworks.com/matlabcentral/fileexchange/10093-fminspleas

[x,y]=readvars('https://www.mathworks.com/matlabcentral/answers/uploaded_files/1034515/data.txt');
funlist={1,@(c,xd) -xd(:).^c};
[c,ab]=fminspleas(funlist, 1 ,x, y);
sol=[ab(:).',c]
sol = 1×3
   -6.5546   -0.0000   -6.0133

2 个评论
显示无隐藏无

Somnath Kale 2022-6-17

@Matt J thank you for your response!

Can you little bit elaborate the code, means fminsplease function and how your calculation that will be god to understand me as well!

Matt J 2022-6-17

编辑：Matt J 2022-6-18

Fminspleas uses a technique which only needs to iterate over the c parameter, so it is an easier search.

请先登录，再进行评论。

Answer 2

Matt J 2022-6-16

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1741910-how-to-resolve-increase-max-function-value-in-fitting-using-fminsearch#answer_987070

编辑：Matt J 2022-6-16

在 MATLAB Online 中打开

If you have the Curve Fitting Toolbox,

[x,y]=readvars('https://www.mathworks.com/matlabcentral/answers/uploaded_files/1034515/data.txt');

ft=fit(x(:),y(:),'power2')

ft =

General model Power2: ft(x) = a*x^b+c Coefficients (with 95% confidence bounds): a = 1.124e-06 (-2.414e-05, 2.639e-05) b = -6.015 (-14.64, 2.609) c = -6.554 (-9.987, -3.121)

plot(ft,x,y)

5 个评论
显示 3更早的评论隐藏 3更早的评论

Matt J 2022-6-17

@Sonnath what is unacceptable about the fit that your current model gives you? You'll notice that both fit() and fminspleas() are in agreement on the fitted parameters.

Somnath Kale 2022-6-17