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 * This help file was generated from butter.sci using help_from_sci().
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<refentry version="5.0-subset Scilab" xml:id="butter" xml:lang="en"
          xmlns="http://docbook.org/ns/docbook"
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  <refnamediv>
    <refname>butter</refname>
    <refpurpose>Design a Butterworth filter.</refpurpose>
  </refnamediv>


<refsynopsisdiv>
   <title>Syntax</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. Order of the Butterworth filter.</para></listitem>
        </varlistentry>
        <varlistentry>
            <term>wc:</term>
            <listitem><para> Positive real value. Normalized digital or analog 3dB cutoff frequency/frequencies.</para></listitem>
        </varlistentry>
        <varlistentry>
            <term>z:</term>
            <listitem><para> Zeros of the filter.</para></listitem>
        </varlistentry>
        <varlistentry>
            <term>p:</term>
            <listitem><para> Poles of the filter.</para></listitem>
        </varlistentry>
        <varlistentry>
            <term>g:</term>
            <listitem><para> Gain of the filter.</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.
If second argument is scalar the third parameter takes in low or high, default value is low. The cutoff is pi*wc radians.
[b,a] = butter(n, [wl, wh]) indicates a band pass filter with cutoffs pi*Wl and pi*wh radians.
[b,a] = butter(n, [wl, wh], ’stop’) indicates a band reject filter with cutoffs pi*wl and pi*wh radians.
[z,p,g] = butter(...) returns filter as zero-pole-gain rather than coefficients of the numerator and denominator polynomials.
[...] = butter(...,’s’) returns a Laplace space filter,here cutoff(s) wc can be larger than 1 (rad/sec).
   </para>
   <para>
</para>
</refsection>

<refsection>
   <title>Examples</title>
   <programlisting role="example"><![CDATA[
[b, a] = butter(4, 0.3, "high")

   ]]></programlisting>
</refsection>
</refentry>
