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Scilab help >> Signal Processing > frfit

# frfit

frequency response fit

### Calling Sequence

sys=frfit(w,fresp,order)
[num,den]=frfit(w,fresp,order)
sys=frfit(w,fresp,order,weight)
[num,den]=frfit(w,fresp,order,weight)

### Arguments

w

positive real vector of frequencies (Hz)

fresp

complex vector of frequency responses (same size as w)

order

integer (required order, degree of den)

weight

positive real vector (default value ones(w)).

num,den

stable polynomials

### Description

sys=frfit(w,fresp,order,weight) returns a bi-stable transfer function G(s)=sys=num/den, of of given order such that its frequency response G(w(i)) matches fresp(i), i.e. freq(num,den,%i*w) should be close to fresp. weight(i) is the weight given to w(i).

### Examples

w=0.01:0.01:2;
s=poly(0,'s');
G=syslin('c',2*(s.^2+0.1*s+2), (s.^2+s+1)*(s.^2+0.3*s+1));
fresp=repfreq(G,w);
Gid=frfit(w,fresp,4);
frespfit=repfreq(Gid,w);
bode(w,[fresp;frespfit])

• frep2tf — transfer function realization from frequency response
• factors — numeric real factorization
• cepstrum — cepstrum calculation
• mrfit — frequency response fit
• freq — frequency response
• calfrq — frequency response discretization