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Parametric identification using xf-orthogonal polynomials.
[num,den] = id_poly(xf,w,nn,nd) [num,den] = id_poly(xf,w,nn,nd,idopt)
A fit of the provided frequency response function xf at the frequency points w is done using a rational fraction of the form H(s)=num(s)/den(s) where num is a polynomial of order nn and den a polynomial of order nd. The numerically well conditioned algorithm proposed in Ref.  is used for this fit.
If more than one frequency response function is provided in xf, the numerator and denominator polynomials are stacked as rows of num and den. The frequency responses corresponding to the identified model can be easily evaluated using the command qbode(num,den,w).
The identification is performed using data within IDopt.SelectedRange. The idcom poly command gives easy access to this function.
id_rc, invfreqs of the Signal Processing Toolbox.