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<a name="Numeric-Data-Types-1"></a>
<h2 class="chapter">4 Numeric Data Types</h2>
<a name="index-numeric-constant-1"></a>
<a name="index-numeric-value-1"></a>
<p>A <em>numeric constant</em> may be a scalar, a vector, or a matrix, and it
may contain complex values.
</p>
<p>The simplest form of a numeric constant, a scalar, is a single number
that can be an integer, a decimal fraction, a number in scientific
(exponential) notation, or a complex number. Note that by default numeric
constants are represented within Octave in double-precision floating
point format (complex constants are stored as pairs of double-precision
floating point values). It is, however, possible to represent real
integers as described in <a href="Integer-Data-Types.html#Integer-Data-Types">Integer Data Types</a>. Here are some
examples of real-valued numeric constants, which all have the same
value:
</p>
<div class="example">
<pre class="example">105
1.05e+2
1050e-1
</pre></div>
<p>To specify complex constants, you can write an expression of the form
</p>
<div class="example">
<pre class="example">3 + 4i
3.0 + 4.0i
0.3e1 + 40e-1i
</pre></div>
<p>all of which are equivalent. The letter ‘<samp>i</samp>’ in the previous example
stands for the pure imaginary constant, defined as
<code>sqrt (-1)</code>.
</p>
<p>For Octave to recognize a value as the imaginary part of a complex
constant, a space must not appear between the number and the ‘<samp>i</samp>’.
If it does, Octave will print an error message, like this:
</p>
<div class="example">
<pre class="example">octave:13> 3 + 4 i
parse error:
syntax error
>>> 3 + 4 i
^
</pre></div>
<p>You may also use ‘<samp>j</samp>’, ‘<samp>I</samp>’, or ‘<samp>J</samp>’ in place of the
‘<samp>i</samp>’ above. All four forms are equivalent.
</p>
<a name="XREFdouble"></a><dl>
<dt><a name="index-double"></a>Built-in Function: <em></em> <strong>double</strong> <em>(<var>x</var>)</em></dt>
<dd><p>Convert <var>x</var> to double precision type.
</p>
<p><strong>See also:</strong> <a href="Single-Precision-Data-Types.html#XREFsingle">single</a>.
</p></dd></dl>
<a name="XREFcomplex"></a><dl>
<dt><a name="index-complex"></a>Built-in Function: <em></em> <strong>complex</strong> <em>(<var>x</var>)</em></dt>
<dt><a name="index-complex-1"></a>Built-in Function: <em></em> <strong>complex</strong> <em>(<var>re</var>, <var>im</var>)</em></dt>
<dd><p>Return a complex result from real arguments. With 1 real argument <var>x</var>,
return the complex result <code><var>x</var> + 0i</code>. With 2 real arguments,
return the complex result <code><var>re</var> + <var>im</var></code>. <code>complex</code> can
often be more convenient than expressions such as <code>a + i*b</code>.
For example:
</p>
<div class="example">
<pre class="example">complex ([1, 2], [3, 4])
⇒ [ 1 + 3i 2 + 4i ]
</pre></div>
<p><strong>See also:</strong> <a href="Complex-Arithmetic.html#XREFreal">real</a>, <a href="Complex-Arithmetic.html#XREFimag">imag</a>, <a href="Predicates-for-Numeric-Objects.html#XREFiscomplex">iscomplex</a>, <a href="Complex-Arithmetic.html#XREFabs">abs</a>, <a href="Complex-Arithmetic.html#XREFarg">arg</a>.
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