<?xml version="1.0" encoding="UTF-8"?>
<!--
 * Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
 * Copyright (C) INRIA -
 * Copyright (C) 2012 - 2016 - Scilab Enterprises
 *
 * This file is hereby licensed under the terms of the GNU GPL v2.0,
 * pursuant to article 5.3.4 of the CeCILL v.2.1.
 * This file was originally licensed under the terms of the CeCILL v2.1,
 * and continues to be available under such terms.
 * For more information, see the COPYING file which you should have received
 * along with this program.
 *
 -->
<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 <emphasis role="bold">(obsolete)</emphasis>
        </refpurpose>
    </refnamediv>
    <refsynopsisdiv>
        <title>Syntax</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>
        <warning>
            <literal>noisegen()</literal> is obsolete. It will be removed from Scilab 6.1.x.
            Please use grand() instead. Examples (clearer, shorter, and more powerful) follow:
            <para/>
            <para>
            100 10-point wide steps with random amplitudes of normal distribution
            of mean 1 and standard deviation 0.7:
            </para>
            <programlisting role="example"><![CDATA[
            u = grand(1,100,"nor",1,0.7) .*. ones(1,10);
            clf, plot(u);
            ]]></programlisting>
            <para/>
            <para>
            40 15-point wide steps with random amplitudes of uniform distribution in [1 3],
            with initial level 0.5 and final level hold:
            </para>
            <programlisting role="example"><![CDATA[
            width = 15;
            u = grand(1,40, "unf", 1, 3) .*. ones(1,width);
            u = [ones(1,8*width)*0.5, u, ones(1,5*width)*u($)];
            clf, plot(u);
            ]]></programlisting>
        </warning>
        <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 &lt;= 0</literal> and
            <literal>t &gt;= 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>
    <refsection role="history">
        <title>History</title>
        <revhistory>
            <revision>
                <revnumber>6.1.0</revnumber>
                <revdescription>
                    noisegen() is obsolete. It will be removed from Scilab 6.1.x.
                    Please replace it with grand() and .*.
                </revdescription>
            </revision>
        </revhistory>
    </refsection>
</refentry>
