Fitting an Amplitude-Response Curve

Question

Chinwe Orie 2019-2-23

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/446544-fitting-an-amplitude-response-curve

评论： Chinwe Orie 2019-3-6

采纳的回答： Rishabh Gupta

Hi,

I'm trying to fit an amplitude-frequency response curve to a particular equation (in picture below).

I've tried using code to do it but I keep getting the following:

f1 = fittype( @(F, w0, g, m, w) F.*(cos(m.*(w0.^2-w.^2)./sqrt(m.^2*(w.^2-w0.^2).^2 + g.^2*w.^2)))....
./sqrt(m.^2*(w.^2-w0.^2).^2 + g.^2*w.^2), 'independent', {'w'},...
'dependent', {'y'} );

Also, I get a warning which says, "Warning: Start point not provided, choosing random start point." What does this mean?

Thanks!

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

Rishabh Gupta 2019-3-4

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/446544-fitting-an-amplitude-response-curve#answer_363656

Hi Chinwe,

Generally Curve Fitting and Optimizations algorithms require you to give a starting point satisfying all your contraints(if any) from where the algorithms starts its logic and tries to find the best fit/best solution. In this case, you did not specify the starting point, hence the warning. But the algorithm needs a starting point, therefore it chooses a random starting point. Howecver this is not an error and may not affect your algorithm/results much. Please note in some case choice of starting point affects the solution.

I hope it was helpful.

Thanks