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.TH mrfit 1 "April 1993" "Scilab Group" "Scilab Function"
.so ../sci.an
.SH NAME
mrfit - frequency response fit
.SH CALLING SEQUENCE
.nf
sys=mrfit(w,mag,order)
[num,den]=mrfit(w,mag,order)
sys=mrfit(w,mag,order,weight)
[num,den]=mrfit(w,mag,order,weight)
.fi
.SH PARAMETERS
.TP 10
w
: positive real vector of frequencies (Hz)
.TP
mag
: real vector of frequency responses magnitude (same size as \fVw\fR)
.TP
order
: integer (required order, degree of \fVden\fR)
.TP
weight
: positive real vector (default value \fVones(w)\fR).
.TP
num,den
: stable polynomials
.SH DESCRIPTION
\fVsys=mrfit(w,mag,order,weight)\fR returns a bi-stable transfer function
\fVG(s)=sys=num/den\fR, of of given \fVorder\fR such that
its frequency response magnitude \fVabs(G(w(i)))\fR
matches \fVmag(i)\fR i.e. \fVabs(freq(num,den,%i*w))\fR should be
close to \fVmag\fR.
\fVweight(i)\fR is the weigth given to \fVw(i)\fR.
.SH EXAMPLE
.nf
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)); // syslin('c',Num,Den);
fresp=repfreq(G,w);
mag=abs(fresp);
Gid=mrfit(w,mag,4);
frespfit=repfreq(Gid,w);
plot2d([w',w'],[mag(:),abs(frespfit(:))])
.fi
.SH SEE ALSO
cepstrum, frfit, freq, calfrq
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