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<?xml version="1.0" encoding="UTF-8"?>
<!--
* Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
* Copyright (C) 2008 - 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-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" version="5.0-subset Scilab" xml:lang="fr" xml:id="rcond">
<info>
<pubdate>$LastChangedDate$</pubdate>
</info>
<refnamediv>
<refname>rcond</refname>
<refpurpose> estimation de l'inverse du conditionnement </refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Séquence d'appel</title>
<synopsis>rcond(X)</synopsis>
</refsynopsisdiv>
<refsection>
<title>Paramètres</title>
<variablelist>
<varlistentry>
<term>X </term>
<listitem>
<para>matrice carrée réelle ou complexe
</para>
</listitem>
</varlistentry>
</variablelist>
</refsection>
<refsection>
<title>Description</title>
<para><literal>rcond(X)</literal> est une estimation de l'inverse du conditionnement de <literal>X</literal> pour la norme l_1.
</para>
<para>
Si <literal>X</literal> est bien conditionnée, <literal>rcond(X)</literal> est proche 1.
Sinon, <literal>rcond(X)</literal> est proche de 0.
</para>
<para><literal>[r,z]=rcond(X)</literal> renvoie <literal>rcond(X)</literal> dans
<literal>r</literal> et renvoie aussi <literal>z</literal> tel que <literal>norm(X*z,1) = r*norm(X,1)*norm(z,1)</literal>
</para>
<para>
Ainsi, si <literal>rcond</literal> est très petit <literal>z</literal> est un vecteur se trouvant dans le noyau de X.
</para>
</refsection>
<refsection>
<title>Exemples</title>
<programlisting role="example"><![CDATA[
A=diag([1:10]);
rcond(A)
A(1,1)=0.000001;
rcond(A)
]]></programlisting>
</refsection>
<refsection>
<title>Voir Aussi</title>
<simplelist type="inline">
<member>
<link linkend="svd">svd</link>
</member>
<member>
<link linkend="cond">cond</link>
</member>
<member>
<link linkend="inv">inv</link>
</member>
</simplelist>
</refsection>
</refentry>
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