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Topic: Is it possible to use high order (>8th) Fourier function for curve fitting
Replies: 0

 Shi Posts: 16 Registered: 12/2/11
Is it possible to use high order (>8th) Fourier function for curve fitting
Posted: Mar 24, 2013 7:32 AM

Hello, everyone:

I have some questions while fitting curves using Fourier function.
The maximum order defined in Matlab itself is 'Fourier8', can I use 9 or 10 order Fourier functions for fitting?

I can construct a anonymous function in my codes, but the problem is it can NOT give a good fitting result. This is same if I define a Fourier8 function by myself.

My understanding is while using 'Fourier8', those coefficients a0,...a8,b1...,b8 are fitting using linear term while w is the nonlinear term.

On the other hand, the use of an anonymous function definition results all coeff are nonlinear term.

My codes here:

ft_ = fittype('fourier8');
% system defined

myFt = myfittype (@(a0,a1,b1,a2,b2,a3,b3,a4,b4,a5,b5,a6,b6,a7,b7,a8,b8,w,x) a0 + a1*cos(x*w) + b1*sin(x*w) + ... +
a10*cos(10*x*w) + b10*sin(10*x*w));
of course there are a2,...a9 and b2,...b8 in the middle but not type here.