help/en_US/ifht.xml


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<?xml version="1.0" encoding="UTF-8"?>

<!--
 *
 * This help file was generated from ifht.sci using help_from_sci().
 *
 -->

<refentry version="5.0-subset Scilab" xml:id="ifht" 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>ifht</refname>
    <refpurpose>Calculate the inverse Fast Hartley Transform of real input D</refpurpose>
  </refnamediv>


<refsynopsisdiv>
   <title>Calling Sequence</title>
   <synopsis>
   m= ifht (d)
   m= ifht (d,n)
   m= ifht (d,n,dim)
   </synopsis>
</refsynopsisdiv>

<refsection>
   <title>Parameters</title>
   <variablelist>
   <varlistentry><term>d:</term>
      <listitem><para> real or complex valued scalar or vector</para></listitem></varlistentry>
   <varlistentry><term>n:</term>
      <listitem><para> Similar to the options of FFT function</para></listitem></varlistentry>
   <varlistentry><term>dim:</term>
      <listitem><para> Similar to the options of FFT function</para></listitem></varlistentry>
   </variablelist>
</refsection>

<refsection>
   <title>Description</title>
   <para>
Calculate the inverse Fast Hartley Transform of real input d. If d is a matrix, the inverse Hartley transform is calculated along the columns by default. The options n and dim are similar to the options of FFT function.
   </para>
   <para>
The forward and inverse Hartley transforms are the same (except for a scale factor of 1/N for the inverse hartley transform), but implemented using different functions.
   </para>
   <para>
The definition of the forward hartley transform for vector d, m[K] = 1/N \sum_{i=0}^{N-1} d[i]*(cos[K*2*pi*i/N] + sin[K*2*pi*i/N]), for 0 &lt;= K &lt; N. m[K] = 1/N \sum_{i=0}^{N-1} d[i]*CAS[K*i], for 0 &lt;= K &lt; N.
</para>
</refsection>

<refsection>
   <title>Examples</title>
   <programlisting role="example"><![CDATA[
ifht(1 : 4)
ifht(1:4, 2)
   ]]></programlisting>
</refsection>
</refentry>