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  <refnamediv>
    <refname>isstable</refname>
    <refpurpose>Check for the stability of a discrete-time system.</refpurpose>
  </refnamediv>


<refsynopsisdiv>
   <title>Syntax</title>
   <synopsis>
   flag = isstable(b, a)
   flag = isstable(sos)
   
   </synopsis>
</refsynopsisdiv>

<refsection>
   <title>Parameters</title>
   <variablelist>
        <varlistentry>
            <term>b:</term>
            <listitem><para> Numerator coefficients of the filter.</para></listitem>
        </varlistentry>
        <varlistentry>
            <term>a:</term>
            <listitem><para> Denominator coefficients of the filter.</para></listitem>
        </varlistentry>
        <varlistentry>
            <term>sos:</term>
            <listitem><para> K x 6 second-order section matrix. Each row corresponds to the coefficients of a second-order filter.</para></listitem>
        </varlistentry>
   </variablelist>
</refsection>

<refsection>
   <title>Description</title>
   <para>
The `isstable` function checks whether a discrete-time system is stable.
A discrete-time system is stable if all poles of the system function are inside the unit circle in the z-plane.
   </para>
   <para>
- When called with `b` and `a`, the function checks the stability of the filter defined by these coefficients.
- When called with `sos`, the function checks the stability of the filter defined by the second-order section matrix.
   </para>
   <para>
The function returns `flag = 1` if the system is stable, and `flag = 0` otherwise.
   </para>
   <para>
</para>
</refsection>

<refsection>
   <title>Examples</title>
   <programlisting role="example"><![CDATA[
flag = isstable([1 2 0], [1 5 6])
   ]]></programlisting>
</refsection>
</refentry>
