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<title>GNU Octave: Missing Data</title>

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<a name="Missing-Data"></a>
<div class="header">
<p>
Next: <a href="String-Objects.html#String-Objects" accesskey="n" rel="next">String Objects</a>, Previous: <a href="Numeric-Objects.html#Numeric-Objects" accesskey="p" rel="prev">Numeric Objects</a>, Up: <a href="Built_002din-Data-Types.html#Built_002din-Data-Types" accesskey="u" rel="up">Built-in Data Types</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>
</div>
<hr>
<a name="Missing-Data-1"></a>
<h4 class="subsection">3.1.2 Missing Data</h4>
<a name="index-missing-data"></a>

<p>It is possible to represent missing data explicitly in Octave using
<code>NA</code> (short for &ldquo;Not Available&rdquo;).  Missing data can only be
represented when data is represented as floating point numbers.  In this
case missing data is represented as a special case of the representation
of <code>NaN</code>.
</p>
<a name="XREFNA"></a><dl>
<dt><a name="index-NA"></a>Built-in Function: <em></em> <strong>NA</strong></dt>
<dt><a name="index-NA-1"></a>Built-in Function: <em></em> <strong>NA</strong> <em>(<var>n</var>)</em></dt>
<dt><a name="index-NA-2"></a>Built-in Function: <em></em> <strong>NA</strong> <em>(<var>n</var>, <var>m</var>)</em></dt>
<dt><a name="index-NA-3"></a>Built-in Function: <em></em> <strong>NA</strong> <em>(<var>n</var>, <var>m</var>, <var>k</var>, &hellip;)</em></dt>
<dt><a name="index-NA-4"></a>Built-in Function: <em></em> <strong>NA</strong> <em>(&hellip;, <var>class</var>)</em></dt>
<dd><p>Return a scalar, matrix, or N-dimensional array whose elements are all equal
to the special constant used to designate missing values.
</p>
<p>Note that NA always compares not equal to NA (NA != NA).
To find NA values, use the <code>isna</code> function.
</p>
<p>When called with no arguments, return a scalar with the value &lsquo;<samp>NA</samp>&rsquo;.
</p>
<p>When called with a single argument, return a square matrix with the dimension
specified.
</p>
<p>When called with more than one scalar argument the first two arguments are
taken as the number of rows and columns and any further arguments specify
additional matrix dimensions.
</p>
<p>The optional argument <var>class</var> specifies the return type and may be
either <code>&quot;double&quot;</code> or <code>&quot;single&quot;</code>.
</p>
<p><strong>See also:</strong> <a href="#XREFisna">isna</a>.
</p></dd></dl>


<a name="XREFisna"></a><dl>
<dt><a name="index-isna"></a>Mapping Function: <em></em> <strong>isna</strong> <em>(<var>x</var>)</em></dt>
<dd><p>Return a logical array which is true where the elements of <var>x</var> are
NA (missing) values and false where they are not.
</p>
<p>For example:
</p>
<div class="example">
<pre class="example">isna ([13, Inf, NA, NaN])
     &rArr; [ 0, 0, 1, 0 ]
</pre></div>

<p><strong>See also:</strong> <a href="Finding-Elements-and-Checking-Conditions.html#XREFisnan">isnan</a>, <a href="Finding-Elements-and-Checking-Conditions.html#XREFisinf">isinf</a>, <a href="Finding-Elements-and-Checking-Conditions.html#XREFisfinite">isfinite</a>.
</p></dd></dl>


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Next: <a href="String-Objects.html#String-Objects" accesskey="n" rel="next">String Objects</a>, Previous: <a href="Numeric-Objects.html#Numeric-Objects" accesskey="p" rel="prev">Numeric Objects</a>, Up: <a href="Built_002din-Data-Types.html#Built_002din-Data-Types" accesskey="u" rel="up">Built-in Data Types</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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