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<a name="Sets"></a>
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Next: <a href="Polynomial-Manipulations.html#Polynomial-Manipulations" accesskey="n" rel="next">Polynomial Manipulations</a>, Previous: <a href="Statistics.html#Statistics" accesskey="p" rel="prev">Statistics</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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<hr>
<a name="Sets-1"></a>
<h2 class="chapter">27 Sets</h2>

<p>Octave has a number of functions for managing sets of data.  A set is defined
as a collection of unique elements and is typically represented by a vector of
numbers sorted in ascending order.  Any vector or matrix can be converted to a
set by removing duplicates through the use of the <code>unique</code> function.
However, it isn&rsquo;t necessary to explicitly create a set as all of the functions
which operate on sets will convert their input to a set before proceeding.
</p>
<a name="XREFunique"></a><dl>
<dt><a name="index-unique"></a>Function File: <em></em> <strong>unique</strong> <em>(<var>x</var>)</em></dt>
<dt><a name="index-unique-1"></a>Function File: <em></em> <strong>unique</strong> <em>(<var>x</var>, &quot;rows&quot;)</em></dt>
<dt><a name="index-unique-2"></a>Function File: <em>[<var>y</var>, <var>i</var>, <var>j</var>] =</em> <strong>unique</strong> <em>(&hellip;)</em></dt>
<dt><a name="index-unique-3"></a>Function File: <em>[<var>y</var>, <var>i</var>, <var>j</var>] =</em> <strong>unique</strong> <em>(&hellip;, &quot;first&quot;)</em></dt>
<dt><a name="index-unique-4"></a>Function File: <em>[<var>y</var>, <var>i</var>, <var>j</var>] =</em> <strong>unique</strong> <em>(&hellip;, &quot;last&quot;)</em></dt>
<dd><p>Return the unique elements of <var>x</var> sorted in ascending order.
</p>
<p>If the input <var>x</var> is a column vector then return a column vector;
Otherwise, return a row vector.  <var>x</var> may also be a cell array of strings.
</p>
<p>If the optional argument <code>&quot;rows&quot;</code> is given then return the unique
rows of <var>x</var> sorted in ascending order.  The input must be a 2-D matrix
to use this option.
</p>
<p>If requested, return index vectors <var>i</var> and <var>j</var> such that
<code><var>y</var> = <var>x</var>(<var>i</var>)</code> and <code><var>x</var> = <var>y</var>(<var>j</var>)</code>.
</p>
<p>Additionally, if <var>i</var> is a requested output then one of <code>&quot;first&quot;</code> or
<code>&quot;last&quot;</code> may be given as an input.  If <code>&quot;last&quot;</code> is specified,
return the highest possible indices in <var>i</var>, otherwise, if <code>&quot;first&quot;</code>
is specified, return the lowest.  The default is <code>&quot;last&quot;</code>.
</p>
<p><strong>See also:</strong> <a href="Set-Operations.html#XREFunion">union</a>, <a href="Set-Operations.html#XREFintersect">intersect</a>, <a href="Set-Operations.html#XREFsetdiff">setdiff</a>, <a href="Set-Operations.html#XREFsetxor">setxor</a>, <a href="Set-Operations.html#XREFismember">ismember</a>.
</p></dd></dl>


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<tr><td align="left" valign="top">&bull; <a href="Set-Operations.html#Set-Operations" accesskey="1">Set Operations</a>:</td><td>&nbsp;&nbsp;</td><td align="left" valign="top">
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