Curve Fitting for a Rational Polynomial Model.

Dear all,

I want to find the best rational Polynomial model that can fit the data shown.

any help would be appreciated.

Data are in dB.

[Mathieu NOE]

hello

looks like a first order low pass (according to the initial slope) followed by a second order resonating TF

what is the issue here ?

[Mohammad]

Hi sorry for late reply I want to find the expression of the polynomials in s domain.

[Alex Sha]

@Mohammad Give out your data please

[Mohammad]

I have uploaded them in the question. thanks

[Sam Chak]

Hey @Mohammad, Is it common practice to describe the frequency response curve of a typical Linear Time-Invariant (LTI) system using elementary functions, as a way to identify the system?

sys = ss([0 1; -400 -2], [0; 1], [1 0], 0);
G   = tf(sys) + tf(1, [1/0.01 1]);
bode(G, {1e-1, 1e2}), grid on