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<?xml version="1.0" encoding="UTF-8"?>
<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="en" xml:id="empty">
<info>
<pubdate>$LastChangedDate$</pubdate>
</info>
<refnamediv>
<refname>empty</refname>
<refpurpose> ([]) empty matrix</refpurpose>
</refnamediv>
<refsection>
<title>Description</title>
<para><literal> [] </literal> denotes the empty matrix. It is uniquely defined
and has 0 row and 0 column, i.e. <literal> size([]) =[0,0] </literal>.
The following convenient conventions are made:</para>
<para>
<literal> [] * A = A * [] = [] </literal>
</para>
<para>
<literal> [] + A = A + [] = A</literal>
</para>
<para>
[ [], A] = [A, []] = A
<literal> inv([]) =[] </literal></para>
<para>
<literal> det([])=cond([])=rcond([])=1, rank([])=0</literal>
</para>
<para>
Matrix functions return <literal>[]</literal> or an error message
when there is no obvious answer. Empty linear systems
(<literal> syslin</literal> lists) may have several rows or columns.</para>
</refsection>
<refsection>
<title>Examples</title>
<programlisting role="example"><![CDATA[
s=poly(0,'s'); A = [s, s+1];
A+[], A*[]
A=rand(2,2); AA=A([],1), size(AA)
svd([])
w=ssrand(2,2,2); wr=[]*w; size(wr), w1=ss2tf(wr), size(w1)
]]></programlisting>
</refsection>
<refsection>
<title>See Also</title>
<simplelist type="inline">
<member>
<link linkend="matrices">matrices</link>
</member>
<member>
<link linkend="poly">poly</link>
</member>
<member>
<link linkend="string">string</link>
</member>
<member>
<link linkend="boolean">boolean</link>
</member>
<member>
<link linkend="rational">rational</link>
</member>
<member>
<link linkend="syslin">syslin</link>
</member>
</simplelist>
</refsection>
</refentry>
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