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<?xml version="1.0" encoding="UTF-8"?>
<!--
* Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
* Copyright (C) 2013 - Scilab Enterprises - Paul Bignier
*
* 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="ifftshift">
<refnamediv>
<refname>ifftshift</refname>
<refpurpose>inverse of fftshift</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Syntax</title>
<synopsis>y=ifftshift(x)</synopsis>
</refsynopsisdiv>
<refsection>
<title>Arguments</title>
<variablelist>
<varlistentry>
<term>x, y</term>
<listitem>
<para>real or complex vector or matrix.</para>
</listitem>
</varlistentry>
</variablelist>
</refsection>
<refsection>
<title>Description</title>
<para>
<literal>ifftshift(x)</literal> swaps the left and right halves of the vector <literal>x</literal>.
</para>
<para>
For matrices, <literal>ifftshift(x)</literal> swaps the first quadrant with the third and the second quadrant with the fourth.
</para>
<para>
If <literal>x</literal> is a multidimensional array,
<literal>ifftshift(x)</literal> swaps "half-spaces" of <literal>x</literal> along each dimension.
</para>
</refsection>
<refsection>
<title>Examples</title>
<para>
Example #1:
</para>
<programlisting role="example"><![CDATA[
// Make a signal
t = 0:0.1:1000;
x = 3*sin(t)+8*sin(3*t)+0.5*sin(5*t)+3*rand(t);
// Compute the fft
y = fft(x, -1);
// Invert the result
shift = fftshift(y);
// Invert the inverted result
invShift = ifftshift(shift);
// Check that we recreated the original result
and(y == invShift)
]]></programlisting>
<para>
Example #2:
</para>
<programlisting role="example"><![CDATA[
// Make a 2D image
t = 0:0.1:30;
x = 3*sin(t')*cos(2*t)+8*sin(3*t')*sin(5*t)+..
0.5*sin(5*t')*sin(5*t)+3*rand(t')*rand(t);
// Compute the fft
y = fft(x,-1);
// Invert the result
shift = fftshift(y);
// Invert the inverted result
invShift = ifftshift(shift);
// Check that we recreated the original result
and(y == invShift)
]]></programlisting>
</refsection>
<refsection role="see also">
<title>See also</title>
<simplelist type="inline">
<member>
<link linkend="fftshift">fftshift</link>
</member>
<member>
<link linkend="fft">fft</link>
</member>
</simplelist>
</refsection>
</refentry>
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