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Aide de Scilab >> Traitement du Signal > 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])```