How to find the best fit coefficients for an equation which is dependant on more than one varying input parameters?

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Nadia A 2016-5-26

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评论： Nadia A 2019-8-14

采纳的回答： Walter Roberson

I am working on finding the coefficients of an equation which is dependant on 3 parameters.

Example: y(t)=exp(a(t)).x(1)+b(t).x(2)+exp(c(t)).exp(c(t)).x(3);

a,b,c are parameters and x(1),x(2),x(3) are coefficients. Parameters are form of a matrix. I need to find the best fit for the coefficients x(1),x(2),x(3).

which function should I use?

Thanks in advance

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Walter Roberson 2016-5-26

在 MATLAB Online 中打开

In the code fragment

b(t).x(2)

what does the character between the ")" and the "x" mean?

Nadia A 2016-5-26

Yes it is multiplication that I meant here. Sorry for the confusion.

I am not able to use the curve fitting toolbox. Shows this error when I tried using it:

To use 'fittype', you might need: fittype - Curve Fitting Toolbox

Is ther any other function I can use to find the coefficients?

Thanks

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采纳的回答

Walter Roberson 2016-5-26

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https://ww2.mathworks.cn/matlabcentral/answers/285876-how-to-find-the-best-fit-coefficients-for-an-equation-which-is-dependant-on-more-than-one-varying-in#answer_223468

If you have the curve fitting toolbox, use fittype() to create the fit parameters and then use fit()

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Muhammet Mammetkuliyev 2019-8-13

Hi Nadia

so how did you solve this fitting problem? I have the same type of fitting to do but dont know how to do it.

thanks

Muhammet Mammetkuliyev 2019-8-14

I am wondering what if equation is not linear in x1, x2 and x3 which are fit parameters?

specifically, I have such equation that I want to fit.

y(t) = abs( a(t)*(x1*exp(1i*x2)+x3/(t-x4+ix5)) )^2

How can I proceed?

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