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<?xml version="1.0" encoding="UTF-8"?>
<!--
*
* This help file was generated from invfreqz.sci using help_from_sci().
*
-->
<refentry version="5.0-subset Scilab" xml:id="invfreqz" xml:lang="en"
xmlns="http://docbook.org/ns/docbook"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:svg="http://www.w3.org/2000/svg"
xmlns:ns3="http://www.w3.org/1999/xhtml"
xmlns:mml="http://www.w3.org/1998/Math/MathML"
xmlns:scilab="http://www.scilab.org"
xmlns:db="http://docbook.org/ns/docbook">
<refnamediv>
<refname>invfreqz</refname>
<refpurpose>Fit filter B(z)/A(z)to the complex frequency response H at frequency points F. A and B are real polynomial coefficients of order nA and nB.</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Calling Sequence</title>
<synopsis>
[B,A,C] = invfreqz(H,F,nB,nA,W,iter,tol,trace)
[B,A,C] = invfreqz(H,F,nB,nA,W)
[B,A,C] = invfreqz(H,F,nB,nA)
</synopsis>
</refsynopsisdiv>
<refsection>
<title>Parameters</title>
<variablelist>
<varlistentry><term>H:</term>
<listitem><para> desired complex frequency response.</para></listitem></varlistentry>
<varlistentry><term>F:</term>
<listitem><para> frequency (must be same length as H).</para></listitem></varlistentry>
<varlistentry><term>nB:</term>
<listitem><para> order of the numerator polynomial B.</para></listitem></varlistentry>
<varlistentry><term>nA:</term>
<listitem><para> order of the denominator polynomial A.</para></listitem></varlistentry>
<varlistentry><term>W:</term>
<listitem><para> vector of weights (must be same length as F).</para></listitem></varlistentry>
</variablelist>
</refsection>
<refsection>
<title>Description</title>
<para>
This is an Octave function.
Fit filter B(z)/A(z)to the complex frequency response H at frequency points F. A and B are real polynomial coefficients of order nA and nB.
Optionally, the fit-errors can be weighted vs frequency according to the weights W.
Note: all the guts are in invfreq.m
</para>
</refsection>
<refsection>
<title>Examples</title>
<programlisting role="example"><![CDATA[
[B,A] = butter(4,1/4);
[H,F] = freqz(B,A);
[Bh,Ah,C] = invfreq(H,F,4,4)
Bh =
0.010209 0.040838 0.061257 0.040838 0.010209
Ah =
1.00000 -1.96843 1.73586 -0.72447 0.12039
C = -7.7065e-15
]]></programlisting>
</refsection>
</refentry>
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