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<?xml version="1.0" encoding="UTF-8"?>
<!--
* Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
* Copyright (C) INRIA -
*
* This file must be used under the terms of the CeCILL.
* This source file is licensed as described in the file COPYING, which
* you should have received as part of this distribution. The terms
* are also available at
* http://www.cecill.info/licences/Licence_CeCILL_V2.1-en.txt
*
-->
<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:svg="http://www.w3.org/2000/svg" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:db="http://docbook.org/ns/docbook" xmlns:scilab="http://www.scilab.org" xml:lang="en" xml:id="noisegen">
<refnamediv>
<refname>noisegen</refname>
<refpurpose>noise generation</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Calling Sequence</title>
<synopsis>b = noisegen(pas, Tmax, sig)</synopsis>
</refsynopsisdiv>
<refsection>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term>pas</term>
<listitem>
<para>real scalar, the time increment</para>
</listitem>
</varlistentry>
<varlistentry>
<term>Tmax</term>
<listitem>
<para>real scalar, the final time of the interval of noise generation</para>
</listitem>
</varlistentry>
<varlistentry>
<term>sig</term>
<listitem>
<para>real scalar, the standard deviation of the noise</para>
</listitem>
</varlistentry>
</variablelist>
</refsection>
<refsection>
<title>Description</title>
<para>
<literal>noisegen()</literal> generates a Scilab function <literal>b = Noise(t)</literal>
where <literal>Noise(t)</literal> is a piecewise constant function
(constant on <literal>[k*pas, (k+1)*pas]</literal>). The value on each constant
interval are random values from i.i.d Gaussian variables of
standard deviation <literal>sig</literal>. The function is constant for <literal>t <= 0</literal> and
<literal>t >= Tmax</literal>.
</para>
<para>
<note>
Note: Random number generator functions such as <link linkend="rand">rand</link> and
<link linkend="grand">grand</link> are another alternative to generate noises
from a wide variety of probability distribution (see example 2 below).
</note>
</para>
</refsection>
<refsection>
<title>Examples</title>
<para>
Example #1: noisegen()
</para>
<programlisting role="example"><![CDATA[
noisegen(0.5, 30, 1.0);
x = -5:0.01:35;
y = feval(x, Noise);
plot(x, y);
]]></programlisting>
<scilab:image>
noisegen(0.5, 30, 1.0);
x = -5:0.01:35;
y = feval(x, Noise);
plot(x, y);
</scilab:image>
<para>
Example #2: rand()
</para>
<programlisting role="example"><![CDATA[
// Plot a zero mean gaussian white noise with the variance 1.
// To use a different variance, multiply rand() by the square root of the variance.
t = 0:.5:30;
sig = 1; // Standard deviation of the white gaussian noise
noise = sig*rand(t, "normal");
plot2d2(t, noise);
]]></programlisting>
<scilab:image>
t = 0:.5:30;
sig = 1;
noise = sig*rand(t, "normal");
plot2d2(t, noise)
</scilab:image>
</refsection>
<refsection role="see also">
<title>See Also</title>
<simplelist type="inline">
<member>
<link linkend="rand">rand</link>
</member>
<member>
<link linkend="grand">grand</link>
</member>
</simplelist>
</refsection>
</refentry>
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