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<?xml version="1.0" encoding="UTF-8"?>
<!--
*
* This help file was generated from butter.sci using help_from_sci().
*
-->
<refentry version="5.0-subset Scilab" xml:id="butter" 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>butter</refname>
<refpurpose>Butterworth filter design..</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Calling Sequence</title>
<synopsis>
[b, a] = butter (n, wc)
[b, a] = butter (n, wc, "high")
[b, a] = butter (n, [wl, wh])
[b, a] = butter (n, [wl, wh], "stop")
[z, p, g] = butter (…)
[…] = butter (…, "s")
</synopsis>
</refsynopsisdiv>
<refsection>
<title>Parameters</title>
<variablelist>
<varlistentry><term>n:</term>
<listitem><para> positive integer value (order of filter).</para></listitem></varlistentry>
<varlistentry><term>wc:</term>
<listitem><para> positive real value,</para><para> 1).Normalised digital 3dB cutoff frequency/frequencies for digital filter, in the range [0, 1] {dimensionless}</para><para> 2).Analog 3dB cutoff frequency/frequencies for analog filter, in the range [0, Inf] {rad/sec}</para></listitem></varlistentry>
</variablelist>
</refsection>
<refsection>
<title>Description</title>
<para>
This function generates a Butterworth filter. Default is a discrete space (z) or digital filter using Bilinear transformation from s to z plane.</para>
<para>If second argument is scalar the third parameter takes in low or high, default value is low. The cutoff is pi*wc radians.</para>
<para>[b,a] = butter(n, [wl, wh]) indicates a band pass filter with cutoffs pi*Wl and pi*wh radians. </para>
<para>[b,a] = butter(n, [wl, wh], ’stop’) indicates a band reject filter with cutoffs pi*wl and pi*wh radians.</para>
<para>[z,p,g] = butter(...) returns filter as zero-pole-gain rather than coefficients of the numerator and denominator polynomials.</para>
<para>[...] = butter(...,’s’) returns a Laplace space filter,here cutoff(s) wc can be larger than 1 (rad/sec).
</para>
</refsection>
<refsection>
<title>Examples</title>
<programlisting role="example"><![CDATA[
n = 4;
wc = 0.3;
[b a] = butter(n, wc, "high")
]]></programlisting>
</refsection>
<refsection>
<title>Modified by :</title>
<simplelist type="vert">
<member>Sonu Sharma, RGIT Mumbai (fellow at FOSSEE, IIT Bombay)</member>
</simplelist>
</refsection>
</refentry>
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