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<?xml version="1.0" encoding="UTF-8"?>
<!--
*
* This help file was generated from fftshift1.sci using help_from_sci().
*
-->
<refentry version="5.0-subset Scilab" xml:id="fftshift1" xml:lang="en"
xmlns="http://docbook.org/ns/docbook"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:svg="http://www.w3.org/2000/svg"
xmlns:ns3="http://www.w3.org/1999/xhtml"
xmlns:mml="http://www.w3.org/1998/Math/MathML"
xmlns:scilab="http://www.scilab.org"
xmlns:db="http://docbook.org/ns/docbook">
<refnamediv>
<refname>fftshift1</refname>
<refpurpose>Perform a shift of the vector X, for use with the 'fft1' and 'ifft1' functions, in order the move the frequency 0 to the center of the vector or matrix.</refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Calling Sequence</title>
<synopsis>
fftshift1 (X)
fftshift1 (X, DIM)
</synopsis>
</refsynopsisdiv>
<refsection>
<title>Parameters</title>
<variablelist>
<varlistentry><term>X:</term>
<listitem><para>It is a vector of N elements corresponding to time samples</para></listitem></varlistentry>
<varlistentry><term>DIM:</term>
<listitem><para> The optional DIM argument can be used to limit the dimension along which the permutation occurs</para></listitem></varlistentry>
</variablelist>
</refsection>
<refsection>
<title>Description</title>
<para>
This is an Octave function.
Perform a shift of the vector X, for use with the 'fft1' and 'ifft1' functions, in order the move the frequency 0 to the center of the vector or matrix.
</para>
<para>
If X is a vector of N elements corresponding to N time samples spaced by dt, then 'fftshift1 (fft1 (X))' corresponds to frequencies
</para>
<para>
f = [ -(ceil((N-1)/2):-1:1)*df 0 (1:floor((N-1)/2))*df ]
</para>
<para>
where df = 1 / dt.
</para>
<para>
If X is a matrix, the same holds for rows and columns. If X is an array, then the same holds along each dimension.
</para>
<para>
The optional DIM argument can be used to limit the dimension along
</para>
</refsection>
</refentry>
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