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Previous: <a href="Converting-Strings.html" accesskey="p" rel="prev">Converting Strings</a>, Up: <a href="Strings.html" accesskey="u" rel="up">Strings</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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<h3 class="section" id="Character-Class-Functions-1"><span>5.5 Character Class Functions<a class="copiable-link" href="#Character-Class-Functions-1"> ¶</a></span></h3>
<p>Octave also provides the following character class test functions
patterned after the functions in the standard C library. They all
operate on string arrays and return matrices of zeros and ones.
Elements that are nonzero indicate that the condition was true for the
corresponding character in the string array. For example:
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">isalpha ("!Q@WERT^Y&")
⇒ [ 0, 1, 0, 1, 1, 1, 1, 0, 1, 0 ]
</pre></div></div>
<a class="anchor" id="XREFisalnum"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-isalnum"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">isalnum</strong> <code class="def-code-arguments">(<var class="var">s</var>)</code><a class="copiable-link" href="#index-isalnum"> ¶</a></span></dt>
<dd><p>Return a logical array which is true where the elements of <var class="var">s</var> are
letters or digits and false where they are not.
</p>
<p>This is equivalent to (<code class="code">isalpha (<var class="var">s</var>) | isdigit (<var class="var">s</var>)</code>).
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFisalpha">isalpha</a>, <a class="ref" href="#XREFisdigit">isdigit</a>, <a class="ref" href="#XREFispunct">ispunct</a>, <a class="ref" href="#XREFisspace">isspace</a>, <a class="ref" href="#XREFiscntrl">iscntrl</a>.
</p></dd></dl>
<a class="anchor" id="XREFisalpha"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-isalpha"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">isalpha</strong> <code class="def-code-arguments">(<var class="var">s</var>)</code><a class="copiable-link" href="#index-isalpha"> ¶</a></span></dt>
<dd><p>Return a logical array which is true where the elements of <var class="var">s</var> are
letters and false where they are not.
</p>
<p>This is equivalent to (<code class="code">islower (<var class="var">s</var>) | isupper (<var class="var">s</var>)</code>).
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFisdigit">isdigit</a>, <a class="ref" href="#XREFispunct">ispunct</a>, <a class="ref" href="#XREFisspace">isspace</a>, <a class="ref" href="#XREFiscntrl">iscntrl</a>, <a class="ref" href="#XREFisalnum">isalnum</a>, <a class="ref" href="#XREFislower">islower</a>, <a class="ref" href="#XREFisupper">isupper</a>.
</p></dd></dl>
<a class="anchor" id="XREFisletter"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-isletter"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">isletter</strong> <code class="def-code-arguments">(<var class="var">s</var>)</code><a class="copiable-link" href="#index-isletter"> ¶</a></span></dt>
<dd><p>Return a logical array which is true where the elements of <var class="var">s</var>
are letters and false where they are not.
</p>
<p>This is an alias for the <code class="code">isalpha</code> function.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFisalpha">isalpha</a>, <a class="ref" href="#XREFisdigit">isdigit</a>, <a class="ref" href="#XREFispunct">ispunct</a>, <a class="ref" href="#XREFisspace">isspace</a>, <a class="ref" href="#XREFiscntrl">iscntrl</a>, <a class="ref" href="#XREFisalnum">isalnum</a>.
</p></dd></dl>
<a class="anchor" id="XREFislower"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-islower"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">islower</strong> <code class="def-code-arguments">(<var class="var">s</var>)</code><a class="copiable-link" href="#index-islower"> ¶</a></span></dt>
<dd><p>Return a logical array which is true where the elements of <var class="var">s</var> are
lowercase letters and false where they are not.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFisupper">isupper</a>, <a class="ref" href="#XREFisalpha">isalpha</a>, <a class="ref" href="#XREFisletter">isletter</a>, <a class="ref" href="#XREFisalnum">isalnum</a>.
</p></dd></dl>
<a class="anchor" id="XREFisupper"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-isupper"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">isupper</strong> <code class="def-code-arguments">(<var class="var">s</var>)</code><a class="copiable-link" href="#index-isupper"> ¶</a></span></dt>
<dd><p>Return a logical array which is true where the elements of <var class="var">s</var> are
uppercase letters and false where they are not.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFislower">islower</a>, <a class="ref" href="#XREFisalpha">isalpha</a>, <a class="ref" href="#XREFisletter">isletter</a>, <a class="ref" href="#XREFisalnum">isalnum</a>.
</p></dd></dl>
<a class="anchor" id="XREFisdigit"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-isdigit"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">isdigit</strong> <code class="def-code-arguments">(<var class="var">s</var>)</code><a class="copiable-link" href="#index-isdigit"> ¶</a></span></dt>
<dd><p>Return a logical array which is true where the elements of <var class="var">s</var> are
decimal digits (0-9) and false where they are not.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFisxdigit">isxdigit</a>, <a class="ref" href="#XREFisalpha">isalpha</a>, <a class="ref" href="#XREFisletter">isletter</a>, <a class="ref" href="#XREFispunct">ispunct</a>, <a class="ref" href="#XREFisspace">isspace</a>, <a class="ref" href="#XREFiscntrl">iscntrl</a>.
</p></dd></dl>
<a class="anchor" id="XREFisxdigit"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-isxdigit"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">isxdigit</strong> <code class="def-code-arguments">(<var class="var">s</var>)</code><a class="copiable-link" href="#index-isxdigit"> ¶</a></span></dt>
<dd><p>Return a logical array which is true where the elements of <var class="var">s</var> are
hexadecimal digits (0-9 and a-fA-F).
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFisdigit">isdigit</a>.
</p></dd></dl>
<a class="anchor" id="XREFispunct"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-ispunct"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">ispunct</strong> <code class="def-code-arguments">(<var class="var">s</var>)</code><a class="copiable-link" href="#index-ispunct"> ¶</a></span></dt>
<dd><p>Return a logical array which is true where the elements of <var class="var">s</var> are
punctuation characters and false where they are not.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFisalpha">isalpha</a>, <a class="ref" href="#XREFisdigit">isdigit</a>, <a class="ref" href="#XREFisspace">isspace</a>, <a class="ref" href="#XREFiscntrl">iscntrl</a>.
</p></dd></dl>
<a class="anchor" id="XREFisspace"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-isspace"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">isspace</strong> <code class="def-code-arguments">(<var class="var">s</var>)</code><a class="copiable-link" href="#index-isspace"> ¶</a></span></dt>
<dd><p>Return a logical array which is true where the elements of <var class="var">s</var> are
whitespace characters (space, formfeed, newline, carriage return, tab, and
vertical tab) and false where they are not.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFiscntrl">iscntrl</a>, <a class="ref" href="#XREFispunct">ispunct</a>, <a class="ref" href="#XREFisalpha">isalpha</a>, <a class="ref" href="#XREFisdigit">isdigit</a>.
</p></dd></dl>
<a class="anchor" id="XREFiscntrl"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-iscntrl"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">iscntrl</strong> <code class="def-code-arguments">(<var class="var">s</var>)</code><a class="copiable-link" href="#index-iscntrl"> ¶</a></span></dt>
<dd><p>Return a logical array which is true where the elements of <var class="var">s</var> are
control characters and false where they are not.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFispunct">ispunct</a>, <a class="ref" href="#XREFisspace">isspace</a>, <a class="ref" href="#XREFisalpha">isalpha</a>, <a class="ref" href="#XREFisdigit">isdigit</a>.
</p></dd></dl>
<a class="anchor" id="XREFisgraph"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-isgraph"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">isgraph</strong> <code class="def-code-arguments">(<var class="var">s</var>)</code><a class="copiable-link" href="#index-isgraph"> ¶</a></span></dt>
<dd><p>Return a logical array which is true where the elements of <var class="var">s</var> are
printable characters (but not the space character) and false where they are
not.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFisprint">isprint</a>.
</p></dd></dl>
<a class="anchor" id="XREFisprint"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-isprint"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">isprint</strong> <code class="def-code-arguments">(<var class="var">s</var>)</code><a class="copiable-link" href="#index-isprint"> ¶</a></span></dt>
<dd><p>Return a logical array which is true where the elements of <var class="var">s</var> are
printable characters (including the space character) and false where they
are not.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFisgraph">isgraph</a>.
</p></dd></dl>
<a class="anchor" id="XREFisascii"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-isascii"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">isascii</strong> <code class="def-code-arguments">(<var class="var">s</var>)</code><a class="copiable-link" href="#index-isascii"> ¶</a></span></dt>
<dd><p>Return a logical array which is true where the elements of <var class="var">s</var> are
ASCII characters (in the range 0 to 127 decimal) and false where they are
not.
</p></dd></dl>
<a class="anchor" id="XREFisstrprop"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-isstrprop"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">isstrprop</strong> <code class="def-code-arguments">(<var class="var">str</var>, <var class="var">prop</var>)</code><a class="copiable-link" href="#index-isstrprop"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-isstrprop-1"><span><code class="def-type"><var class="var">tf</var> =</code> <strong class="def-name">isstrprop</strong> <code class="def-code-arguments">(<var class="var">str</var>, <var class="var">prop</var>, 'ForceCellOutput', <var class="var">flag</var>)</code><a class="copiable-link" href="#index-isstrprop-1"> ¶</a></span></dt>
<dd><p>Test character string properties.
</p>
<p>For example:
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">isstrprop ("abc123", "alpha")
⇒ [1, 1, 1, 0, 0, 0]
</pre></div></div>
<p>If <var class="var">str</var> is a cell array, <code class="code">isstrpop</code> is applied recursively to
each element of the cell array.
</p>
<p>Numeric arrays are converted to character strings.
</p>
<p>The second argument <var class="var">prop</var> must be one of
</p>
<dl class="table">
<dt><code class="code">"alpha"</code></dt>
<dd><p>True for characters that are alphabetic (letters).
</p>
</dd>
<dt><code class="code">"alnum"</code></dt>
<dt><code class="code">"alphanum"</code></dt>
<dd><p>True for characters that are alphabetic or digits.
</p>
</dd>
<dt><code class="code">"lower"</code></dt>
<dd><p>True for lowercase letters.
</p>
</dd>
<dt><code class="code">"upper"</code></dt>
<dd><p>True for uppercase letters.
</p>
</dd>
<dt><code class="code">"digit"</code></dt>
<dd><p>True for decimal digits (0-9).
</p>
</dd>
<dt><code class="code">"xdigit"</code></dt>
<dd><p>True for hexadecimal digits (a-fA-F0-9).
</p>
</dd>
<dt><code class="code">"space"</code></dt>
<dt><code class="code">"wspace"</code></dt>
<dd><p>True for whitespace characters (space, formfeed, newline, carriage return,
tab, vertical tab).
</p>
</dd>
<dt><code class="code">"punct"</code></dt>
<dd><p>True for punctuation characters (printing characters except space or
letter or digit).
</p>
</dd>
<dt><code class="code">"cntrl"</code></dt>
<dd><p>True for control characters.
</p>
</dd>
<dt><code class="code">"graph"</code></dt>
<dt><code class="code">"graphic"</code></dt>
<dd><p>True for printing characters except space.
</p>
</dd>
<dt><code class="code">"print"</code></dt>
<dd><p>True for printing characters including space.
</p>
</dd>
<dt><code class="code">"ascii"</code></dt>
<dd><p>True for characters that are in the range of ASCII encoding.
</p>
</dd>
</dl>
<p>If the option <code class="code">'ForceCellOutput'</code> is given and <var class="var">flag</var> is
true then a cell value is returned rather than a logical array.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFisalpha">isalpha</a>, <a class="ref" href="#XREFisalnum">isalnum</a>, <a class="ref" href="#XREFislower">islower</a>, <a class="ref" href="#XREFisupper">isupper</a>, <a class="ref" href="#XREFisdigit">isdigit</a>, <a class="ref" href="#XREFisxdigit">isxdigit</a>, <a class="ref" href="#XREFisspace">isspace</a>, <a class="ref" href="#XREFispunct">ispunct</a>, <a class="ref" href="#XREFiscntrl">iscntrl</a>, <a class="ref" href="#XREFisgraph">isgraph</a>, <a class="ref" href="#XREFisprint">isprint</a>, <a class="ref" href="#XREFisascii">isascii</a>.
</p></dd></dl>
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