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
Nadia A 2016-5-26
评论： Nadia A 2019-8-14
Hi
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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Nadia A
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
Walter Roberson 2016-5-26
If you have the curve fitting toolbox, use fittype() to create the fit parameters and then use fit()
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Muhammet Mammetkuliyev
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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Muhammet Mammetkuliyev
and one like this
y(t) = abs( x1*exp(1i*x2)+a(t)(x3/(t-x4+ix5)) + b(t)*(x6/(t-x7+ix8)))^2

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