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<a name="Logical-Values"></a>
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Next: <a href="Promotion-and-Demotion-of-Data-Types.html#Promotion-and-Demotion-of-Data-Types" accesskey="n" rel="next">Promotion and Demotion of Data Types</a>, Previous: <a href="Bit-Manipulations.html#Bit-Manipulations" accesskey="p" rel="prev">Bit Manipulations</a>, Up: <a href="Numeric-Data-Types.html#Numeric-Data-Types" accesskey="u" rel="up">Numeric Data Types</a> [<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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<a name="Logical-Values-1"></a>
<h3 class="section">4.6 Logical Values</h3>
<p>Octave has built-in support for logical values, i.e., variables that
are either <code>true</code> or <code>false</code>. When comparing two variables,
the result will be a logical value whose value depends on whether or
not the comparison is true.
</p>
<p>The basic logical operations are <code>&</code>, <code>|</code>, and <code>!</code>,
which correspond to “Logical And”, “Logical Or”, and “Logical
Negation”. These operations all follow the usual rules of logic.
</p>
<p>It is also possible to use logical values as part of standard numerical
calculations. In this case <code>true</code> is converted to <code>1</code>, and
<code>false</code> to 0, both represented using double precision floating
point numbers. So, the result of <code>true*22 - false/6</code> is <code>22</code>.
</p>
<p>Logical values can also be used to index matrices and cell arrays.
When indexing with a logical array the result will be a vector containing
the values corresponding to <code>true</code> parts of the logical array.
The following example illustrates this.
</p>
<div class="example">
<pre class="example">data = [ 1, 2; 3, 4 ];
idx = (data <= 2);
data(idx)
⇒ ans = [ 1; 2 ]
</pre></div>
<p>Instead of creating the <code>idx</code> array it is possible to replace
<code>data(idx)</code> with <code>data( data <= 2 )</code><!-- /@w --> in the above code.
</p>
<p>Logical values can also be constructed by
casting numeric objects to logical values, or by using the <code>true</code>
or <code>false</code> functions.
</p>
<a name="XREFlogical"></a><dl>
<dt><a name="index-logical"></a><em></em> <strong>logical</strong> <em>(<var>x</var>)</em></dt>
<dd><p>Convert the numeric object <var>x</var> to logical type.
</p>
<p>Any nonzero values will be converted to true (1) while zero values will be
converted to false (0). The non-numeric value NaN cannot be converted and
will produce an error.
</p>
<p>Compatibility Note: Octave accepts complex values as input, whereas
<small>MATLAB</small> issues an error.
</p>
<p><strong>See also:</strong> <a href="Numeric-Data-Types.html#XREFdouble">double</a>, <a href="Single-Precision-Data-Types.html#XREFsingle">single</a>, <a href="Concatenating-Strings.html#XREFchar">char</a>.
</p></dd></dl>
<a name="XREFtrue"></a><dl>
<dt><a name="index-true"></a><em></em> <strong>true</strong> <em>(<var>x</var>)</em></dt>
<dt><a name="index-true-1"></a><em></em> <strong>true</strong> <em>(<var>n</var>, <var>m</var>)</em></dt>
<dt><a name="index-true-2"></a><em></em> <strong>true</strong> <em>(<var>n</var>, <var>m</var>, <var>k</var>, …)</em></dt>
<dd><p>Return a matrix or N-dimensional array whose elements are all logical 1.
</p>
<p>If invoked with a single scalar integer argument, return a square
matrix of the specified size.
</p>
<p>If invoked with two or more scalar integer arguments, or a vector of integer
values, return an array with given dimensions.
</p>
<p><strong>See also:</strong> <a href="#XREFfalse">false</a>.
</p></dd></dl>
<a name="XREFfalse"></a><dl>
<dt><a name="index-false"></a><em></em> <strong>false</strong> <em>(<var>x</var>)</em></dt>
<dt><a name="index-false-1"></a><em></em> <strong>false</strong> <em>(<var>n</var>, <var>m</var>)</em></dt>
<dt><a name="index-false-2"></a><em></em> <strong>false</strong> <em>(<var>n</var>, <var>m</var>, <var>k</var>, …)</em></dt>
<dd><p>Return a matrix or N-dimensional array whose elements are all logical 0.
</p>
<p>If invoked with a single scalar integer argument, return a square
matrix of the specified size.
</p>
<p>If invoked with two or more scalar integer arguments, or a vector of integer
values, return an array with given dimensions.
</p>
<p><strong>See also:</strong> <a href="#XREFtrue">true</a>.
</p></dd></dl>
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