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<title>butter</title>
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<span class="path"><a href="index.html">FOSSEE Signal Processing Toolbox</a> >> <a href="section_e54aa8aac34aa55341e8b4b782fe1a74.html">FOSSEE Signal Processing Toolbox</a> > butter</span>
<br /><br />
<div class="refnamediv"><h1 class="refname">butter</h1>
<p class="refpurpose">This function generates a Butterworth filter.</p></div>
<div class="refsynopsisdiv"><h3 class="title">Calling Sequence</h3>
<div class="synopsis"><pre><span class="default">[</span><span class="default">a</span><span class="default">, </span><span class="default">b</span><span class="default">] = </span><span class="functionid">butter</span><span class="default"> (</span><span class="default">n</span><span class="default">, </span><span class="default">w</span><span class="default">)</span>
<span class="default">[</span><span class="default">a</span><span class="default">, </span><span class="default">b</span><span class="default">] = </span><span class="functionid">butter</span><span class="default"> (</span><span class="default">n</span><span class="default">, </span><span class="default">w</span><span class="default">, </span>"<span class="default">high</span>"<span class="default">)</span>
<span class="default">[</span><span class="default">a</span><span class="default">, </span><span class="default">b</span><span class="default">] = </span><span class="functionid">butter</span><span class="default"> (</span><span class="default">n</span><span class="default">, [</span><span class="default">wl</span><span class="default">, </span><span class="default">wh</span><span class="default">])</span>
<span class="default">[</span><span class="default">b</span><span class="default">, </span><span class="default">a</span><span class="default">] = </span><span class="functionid">butter</span><span class="default"> (</span><span class="default">n</span><span class="default">, [</span><span class="default">wl</span><span class="default">, </span><span class="default">wh</span><span class="default">], </span>"<span class="default">stop</span>"<span class="default">)</span>
<span class="default">[</span><span class="default">a</span><span class="default">, </span><span class="default">b</span><span class="default">, </span><span class="default">c</span><span class="default">] = </span><span class="functionid">butter</span><span class="default"> (…)</span>
<span class="default">[</span><span class="default">a</span><span class="default">, </span><span class="default">b</span><span class="default">, </span><span class="default">c</span><span class="default">, </span><span class="default">d</span><span class="default">] = </span><span class="functionid">butter</span><span class="default"> (…)</span>
<span class="default">[…] = </span><span class="functionid">butter</span><span class="default"> (…, </span>"<span class="default">s</span>"<span class="default">)</span></pre></div></div>
<div class="refsection"><h3 class="title">Parameters</h3>
<dl><dt><span class="term">n:</span>
<dd><p class="para">positive integer value</p></dd></dt>
<dt><span class="term">w:</span>
<dd><p class="para">positive real value, w in the range [0,1]</p></dd></dt></dl></div>
<div class="refsection"><h3 class="title">Description</h3>
<p class="para">This is an Octave function.
This function generates a Butterworth filter. Default is a discrete space (Z) filter.
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 edges pi*Wl and pi*Wh radians.
[b,a] = butter(n, [Wl, Wh], ’stop’) indicates a band reject filter with edges 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, w can be larger than 1.
[a,b,c,d] = butter(...) returns state-space matrices.</p></div>
<div class="refsection"><h3 class="title">Examples</h3>
<div class="programlisting"><table border="0" width="100%"><tr><td width="98%"><pre class="scilabcode"><span class="scilabopenclose">[</span><span class="scilabid">a</span><span class="scilabdefault">,</span><span class="scilabid">b</span><span class="scilabopenclose">]</span><span class="scilaboperator">=</span><span class="scilabid">butter</span><span class="scilabopenclose">(</span><span class="scilabnumber">3</span><span class="scilabdefault">,</span> <span class="scilabnumber">0.7</span><span class="scilabopenclose">)</span>
<span class="scilabid">a</span> <span class="scilaboperator">=</span>
<span class="scilabnumber">0.37445</span> <span class="scilabnumber">1.12336</span> <span class="scilabnumber">1.12336</span> <span class="scilabnumber">0.37445</span>
<span class="scilabid">b</span> <span class="scilaboperator">=</span>
<span class="scilabnumber">1.00000</span> <span class="scilabnumber">1.16192</span> <span class="scilabnumber">0.69594</span> <span class="scilabnumber">0.13776</span></pre></td><td valign="top"><a href="scilab://scilab.execexample/"><img src="ScilabExecute.png" border="0"/></a></td><td valign="top"><a href="scilab://scilab.editexample/"><img src="ScilabEdit.png" border="0"/></a></td><td></td></tr></table></div></div>
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