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<a name="String-Conversions"></a>
<div class="header">
<p>
Next: <a href="Character-Class-Functions.html#Character-Class-Functions" accesskey="n" rel="next">Character Class Functions</a>, Previous: <a href="Manipulating-Strings.html#Manipulating-Strings" accesskey="p" rel="prev">Manipulating Strings</a>, Up: <a href="Strings.html#Strings" 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#Concept-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="String-Conversions-1"></a>
<h3 class="section">5.6 String Conversions</h3>
<p>Octave supports various kinds of conversions between strings and
numbers. As an example, it is possible to convert a string containing
a hexadecimal number to a floating point number.
</p>
<div class="example">
<pre class="example">hex2dec ("FF")
⇒ 255
</pre></div>
<a name="XREFbin2dec"></a><dl>
<dt><a name="index-bin2dec"></a><em></em> <strong>bin2dec</strong> <em>(<var>s</var>)</em></dt>
<dd><p>Return the decimal number corresponding to the binary number represented
by the string <var>s</var>.
</p>
<p>For example:
</p>
<div class="example">
<pre class="example">bin2dec ("1110")
⇒ 14
</pre></div>
<p>Spaces are ignored during conversion and may be used to make the binary
number more readable.
</p>
<div class="example">
<pre class="example">bin2dec ("1000 0001")
⇒ 129
</pre></div>
<p>If <var>s</var> is a string matrix, return a column vector with one converted
number per row of <var>s</var>; Invalid rows evaluate to NaN.
</p>
<p>If <var>s</var> is a cell array of strings, return a column vector with one
converted number per cell element in <var>s</var>.
</p>
<p><strong>See also:</strong> <a href="#XREFdec2bin">dec2bin</a>, <a href="#XREFbase2dec">base2dec</a>, <a href="#XREFhex2dec">hex2dec</a>.
</p></dd></dl>
<a name="XREFdec2bin"></a><dl>
<dt><a name="index-dec2bin"></a><em></em> <strong>dec2bin</strong> <em>(<var>d</var>, <var>len</var>)</em></dt>
<dd><p>Return a binary number corresponding to the non-negative integer <var>d</var>,
as a string of ones and zeros.
</p>
<p>For example:
</p>
<div class="example">
<pre class="example">dec2bin (14)
⇒ "1110"
</pre></div>
<p>If <var>d</var> is a matrix or cell array, return a string matrix with one row
per element in <var>d</var>, padded with leading zeros to the width of the
largest value.
</p>
<p>The optional second argument, <var>len</var>, specifies the minimum number of
digits in the result.
</p>
<p><strong>See also:</strong> <a href="#XREFbin2dec">bin2dec</a>, <a href="#XREFdec2base">dec2base</a>, <a href="#XREFdec2hex">dec2hex</a>.
</p></dd></dl>
<a name="XREFdec2hex"></a><dl>
<dt><a name="index-dec2hex"></a><em></em> <strong>dec2hex</strong> <em>(<var>d</var>, <var>len</var>)</em></dt>
<dd><p>Return the hexadecimal string corresponding to the non-negative integer
<var>d</var>.
</p>
<p>For example:
</p>
<div class="example">
<pre class="example">dec2hex (2748)
⇒ "ABC"
</pre></div>
<p>If <var>d</var> is a matrix or cell array, return a string matrix with one row
per element in <var>d</var>, padded with leading zeros to the width of the
largest value.
</p>
<p>The optional second argument, <var>len</var>, specifies the minimum number of
digits in the result.
</p>
<p><strong>See also:</strong> <a href="#XREFhex2dec">hex2dec</a>, <a href="#XREFdec2base">dec2base</a>, <a href="#XREFdec2bin">dec2bin</a>.
</p></dd></dl>
<a name="XREFhex2dec"></a><dl>
<dt><a name="index-hex2dec"></a><em></em> <strong>hex2dec</strong> <em>(<var>s</var>)</em></dt>
<dd><p>Return the integer corresponding to the hexadecimal number represented by
the string <var>s</var>.
</p>
<p>For example:
</p>
<div class="example">
<pre class="example">hex2dec ("12B")
⇒ 299
hex2dec ("12b")
⇒ 299
</pre></div>
<p>If <var>s</var> is a string matrix, return a column vector with one converted
number per row of <var>s</var>; Invalid rows evaluate to NaN.
</p>
<p>If <var>s</var> is a cell array of strings, return a column vector with one
converted number per cell element in <var>s</var>.
</p>
<p><strong>See also:</strong> <a href="#XREFdec2hex">dec2hex</a>, <a href="#XREFbase2dec">base2dec</a>, <a href="#XREFbin2dec">bin2dec</a>.
</p></dd></dl>
<a name="XREFdec2base"></a><dl>
<dt><a name="index-dec2base"></a><em></em> <strong>dec2base</strong> <em>(<var>d</var>, <var>base</var>)</em></dt>
<dt><a name="index-dec2base-1"></a><em></em> <strong>dec2base</strong> <em>(<var>d</var>, <var>base</var>, <var>len</var>)</em></dt>
<dd><p>Return a string of symbols in base <var>base</var> corresponding to the
non-negative integer <var>d</var>.
</p>
<div class="example">
<pre class="example">dec2base (123, 3)
⇒ "11120"
</pre></div>
<p>If <var>d</var> is a matrix or cell array, return a string matrix with one row
per element in <var>d</var>, padded with leading zeros to the width of the
largest value.
</p>
<p>If <var>base</var> is a string then the characters of <var>base</var> are used as
the symbols for the digits of <var>d</var>. Space (’ ’) may not be used as a
symbol.
</p>
<div class="example">
<pre class="example">dec2base (123, "aei")
⇒ "eeeia"
</pre></div>
<p>The optional third argument, <var>len</var>, specifies the minimum number of
digits in the result.
</p>
<p><strong>See also:</strong> <a href="#XREFbase2dec">base2dec</a>, <a href="#XREFdec2bin">dec2bin</a>, <a href="#XREFdec2hex">dec2hex</a>.
</p></dd></dl>
<a name="XREFbase2dec"></a><dl>
<dt><a name="index-base2dec"></a><em></em> <strong>base2dec</strong> <em>(<var>s</var>, <var>base</var>)</em></dt>
<dd><p>Convert <var>s</var> from a string of digits in base <var>base</var> to a decimal
integer (base 10).
</p>
<div class="example">
<pre class="example">base2dec ("11120", 3)
⇒ 123
</pre></div>
<p>If <var>s</var> is a string matrix, return a column vector with one value per
row of <var>s</var>. If a row contains invalid symbols then the corresponding
value will be NaN.
</p>
<p>If <var>s</var> is a cell array of strings, return a column vector with one
value per cell element in <var>s</var>.
</p>
<p>If <var>base</var> is a string, the characters of <var>base</var> are used as the
symbols for the digits of <var>s</var>. Space (’ ’) may not be used as a symbol.
</p>
<div class="example">
<pre class="example">base2dec ("yyyzx", "xyz")
⇒ 123
</pre></div>
<p><strong>See also:</strong> <a href="#XREFdec2base">dec2base</a>, <a href="#XREFbin2dec">bin2dec</a>, <a href="#XREFhex2dec">hex2dec</a>.
</p></dd></dl>
<a name="XREFnum2hex"></a><dl>
<dt><a name="index-num2hex"></a><em><var>s</var> =</em> <strong>num2hex</strong> <em>(<var>n</var>)</em></dt>
<dt><a name="index-num2hex-1"></a><em><var>s</var> =</em> <strong>num2hex</strong> <em>(<var>n</var>, "cell")</em></dt>
<dd><p>Convert a numeric array to an array of hexadecimal strings.
</p>
<p>For example:
</p>
<div class="example">
<pre class="example">num2hex ([-1, 1, e, Inf])
⇒ "bff0000000000000
3ff0000000000000
4005bf0a8b145769
7ff0000000000000"
</pre></div>
<p>If the argument <var>n</var> is a single precision number or vector, the returned
string has a length of 8. For example:
</p>
<div class="example">
<pre class="example">num2hex (single ([-1, 1, e, Inf]))
⇒ "bf800000
3f800000
402df854
7f800000"
</pre></div>
<p>With the optional second argument <code>"cell"</code>, return a cell array of
strings instead of a character array.
</p>
<p><strong>See also:</strong> <a href="#XREFhex2num">hex2num</a>, <a href="#XREFhex2dec">hex2dec</a>, <a href="#XREFdec2hex">dec2hex</a>.
</p></dd></dl>
<a name="XREFhex2num"></a><dl>
<dt><a name="index-hex2num"></a><em><var>n</var> =</em> <strong>hex2num</strong> <em>(<var>s</var>)</em></dt>
<dt><a name="index-hex2num-1"></a><em><var>n</var> =</em> <strong>hex2num</strong> <em>(<var>s</var>, <var>class</var>)</em></dt>
<dd><p>Typecast a hexadecimal character array or cell array of strings to an
array of numbers.
</p>
<p>By default, the input array is interpreted as a hexadecimal number
representing a double precision value. If fewer than 16 characters are
given the strings are right padded with <code>'0'</code> characters.
</p>
<p>Given a string matrix, <code>hex2num</code> treats each row as a separate number.
</p>
<div class="example">
<pre class="example">hex2num (["4005bf0a8b145769"; "4024000000000000"])
⇒ [2.7183; 10.000]
</pre></div>
<p>The optional second argument <var>class</var> may be used to cause the input
array to be interpreted as a different value type. Possible values are
</p>
<table>
<thead><tr><th>Option</th><th>Characters</th></tr></thead>
<tr><td><code>"int8"</code></td><td>2</td></tr>
<tr><td><code>"uint8"</code></td><td>2</td></tr>
<tr><td><code>"int16"</code></td><td>4</td></tr>
<tr><td><code>"uint16"</code></td><td>4</td></tr>
<tr><td><code>"int32"</code></td><td>8</td></tr>
<tr><td><code>"uint32"</code></td><td>8</td></tr>
<tr><td><code>"int64"</code></td><td>16</td></tr>
<tr><td><code>"uint64"</code></td><td>16</td></tr>
<tr><td><code>"char"</code></td><td>2</td></tr>
<tr><td><code>"single"</code></td><td>8</td></tr>
<tr><td><code>"double"</code></td><td>16</td></tr>
</table>
<p>For example:
</p>
<div class="example">
<pre class="example">hex2num (["402df854"; "41200000"], "single")
⇒ [2.7183; 10.000]
</pre></div>
<p><strong>See also:</strong> <a href="#XREFnum2hex">num2hex</a>, <a href="#XREFhex2dec">hex2dec</a>, <a href="#XREFdec2hex">dec2hex</a>.
</p></dd></dl>
<a name="XREFstr2double"></a><dl>
<dt><a name="index-str2double"></a><em></em> <strong>str2double</strong> <em>(<var>s</var>)</em></dt>
<dd><p>Convert a string to a real or complex number.
</p>
<p>The string must be in one of the following formats where a and b are real
numbers and the complex unit is <code>'i'</code> or <code>'j'</code>:
</p>
<ul>
<li> a + bi
</li><li> a + b*i
</li><li> a + i*b
</li><li> bi + a
</li><li> b*i + a
</li><li> i*b + a
</li></ul>
<p>If present, a and/or b are of the form [+-]d[,.]d[[eE][+-]d] where
the brackets indicate optional arguments and <code>'d'</code> indicates zero or
more digits. The special input values <code>Inf</code>, <code>NaN</code>, and <code>NA</code>
are also accepted.
</p>
<p><var>s</var> may be a character string, character matrix, or cell array. For
character arrays the conversion is repeated for every row, and a double or
complex array is returned. Empty rows in <var>s</var> are deleted and not
returned in the numeric array. For cell arrays each character string
element is processed and a double or complex array of the same dimensions as
<var>s</var> is returned.
</p>
<p>For unconvertible scalar or character string input <code>str2double</code> returns
a NaN. Similarly, for character array input <code>str2double</code> returns a
NaN for any row of <var>s</var> that could not be converted. For a cell array,
<code>str2double</code> returns a NaN for any element of <var>s</var> for which
conversion fails. Note that numeric elements in a mixed string/numeric
cell array are not strings and the conversion will fail for these elements
and return NaN.
</p>
<p><code>str2double</code> can replace <code>str2num</code>, and it avoids the security
risk of using <code>eval</code> on unknown data.
</p>
<p><strong>See also:</strong> <a href="#XREFstr2num">str2num</a>.
</p></dd></dl>
<a name="XREFstrjust"></a><dl>
<dt><a name="index-strjust"></a><em></em> <strong>strjust</strong> <em>(<var>s</var>)</em></dt>
<dt><a name="index-strjust-1"></a><em></em> <strong>strjust</strong> <em>(<var>s</var>, <var>pos</var>)</em></dt>
<dd><p>Return the text, <var>s</var>, justified according to <var>pos</var>, which may
be <code>"left"</code>, <code>"center"</code>, or <code>"right"</code>.
</p>
<p>If <var>pos</var> is omitted it defaults to <code>"right"</code>.
</p>
<p>Null characters are replaced by spaces. All other character data are
treated as non-white space.
</p>
<p>Example:
</p>
<div class="example">
<pre class="example">strjust (["a"; "ab"; "abc"; "abcd"])
⇒
" a"
" ab"
" abc"
"abcd"
</pre></div>
<p><strong>See also:</strong> <a href="Manipulating-Strings.html#XREFdeblank">deblank</a>, <a href="Manipulating-Strings.html#XREFstrrep">strrep</a>, <a href="Manipulating-Strings.html#XREFstrtrim">strtrim</a>, <a href="Manipulating-Strings.html#XREFuntabify">untabify</a>.
</p></dd></dl>
<a name="XREFstr2num"></a><dl>
<dt><a name="index-str2num"></a><em><var>x</var> =</em> <strong>str2num</strong> <em>(<var>s</var>)</em></dt>
<dt><a name="index-str2num-1"></a><em>[<var>x</var>, <var>state</var>] =</em> <strong>str2num</strong> <em>(<var>s</var>)</em></dt>
<dd><p>Convert the string (or character array) <var>s</var> to a number (or an array).
</p>
<p>Examples:
</p>
<div class="example">
<pre class="example">str2num ("3.141596")
⇒ 3.141596
str2num (["1, 2, 3"; "4, 5, 6"])
⇒ 1 2 3
4 5 6
</pre></div>
<p>The optional second output, <var>state</var>, is logically true when the
conversion is successful. If the conversion fails the numeric output,
<var>x</var>, is empty and <var>state</var> is false.
</p>
<p><strong>Caution:</strong> As <code>str2num</code> uses the <code>eval</code> function to do the
conversion, <code>str2num</code> will execute any code contained in the string
<var>s</var>. Use <code>str2double</code> for a safer and faster conversion.
</p>
<p>For cell array of strings use <code>str2double</code>.
</p>
<p><strong>See also:</strong> <a href="#XREFstr2double">str2double</a>, <a href="Evaluation.html#XREFeval">eval</a>.
</p></dd></dl>
<a name="XREFtolower"></a><dl>
<dt><a name="index-tolower"></a><em></em> <strong>tolower</strong> <em>(<var>s</var>)</em></dt>
<dt><a name="index-lower"></a><em></em> <strong>lower</strong> <em>(<var>s</var>)</em></dt>
<dd><p>Return a copy of the string or cell string <var>s</var>, with each uppercase
character replaced by the corresponding lowercase one; non-alphabetic
characters are left unchanged.
</p>
<p>For example:
</p>
<div class="example">
<pre class="example">tolower ("MiXeD cAsE 123")
⇒ "mixed case 123"
</pre></div>
<p><strong>See also:</strong> <a href="#XREFtoupper">toupper</a>.
</p></dd></dl>
<a name="XREFtoupper"></a><dl>
<dt><a name="index-toupper"></a><em></em> <strong>toupper</strong> <em>(<var>s</var>)</em></dt>
<dt><a name="index-upper"></a><em></em> <strong>upper</strong> <em>(<var>s</var>)</em></dt>
<dd><p>Return a copy of the string or cell string <var>s</var>, with each lowercase
character replaced by the corresponding uppercase one; non-alphabetic
characters are left unchanged.
</p>
<p>For example:
</p>
<div class="example">
<pre class="example">toupper ("MiXeD cAsE 123")
⇒ "MIXED CASE 123"
</pre></div>
<p><strong>See also:</strong> <a href="#XREFtolower">tolower</a>.
</p></dd></dl>
<a name="XREFunicode2native"></a><dl>
<dt><a name="index-unicode2native"></a><em><var>native_bytes</var> =</em> <strong>unicode2native</strong> <em>(<var>utf8_str</var>, <var>codepage</var>)</em></dt>
<dt><a name="index-unicode2native-1"></a><em><var>native_bytes</var> =</em> <strong>unicode2native</strong> <em>(<var>utf8_str</var>)</em></dt>
<dd><p>Convert UTF-8 string <var>utf8_str</var> to byte stream using <var>codepage</var>.
</p>
<p>The character vector <var>utf8_str</var> is converted to a byte stream
<var>native_bytes</var> using the code page given by <var>codepage</var>. The
string <var>codepage</var> must be an identifier of a valid code page.
Examples for valid code pages are <code>"ISO-8859-1"</code>,
<code>"Shift-JIS"</code>, or <code>"UTF-16"</code>. For a list of supported code
pages, see <a href="https://www.gnu.org/software/libiconv">https://www.gnu.org/software/libiconv</a>. If <var>codepage</var>
is omitted or empty, the system default codepage is used.
</p>
<p>If any of the characters cannot be mapped into the codepage <var>codepage</var>,
they are replaced with the appropriate substitution sequence for that
codepage.
</p>
<p><strong>See also:</strong> <a href="#XREFnative2unicode">native2unicode</a>.
</p></dd></dl>
<a name="XREFnative2unicode"></a><dl>
<dt><a name="index-native2unicode"></a><em><var>utf8_str</var> =</em> <strong>native2unicode</strong> <em>(<var>native_bytes</var>, <var>codepage</var>)</em></dt>
<dt><a name="index-native2unicode-1"></a><em><var>utf8_str</var> =</em> <strong>native2unicode</strong> <em>(<var>native_bytes</var>)</em></dt>
<dd><p>Convert byte stream <var>native_bytes</var> to UTF-8 using <var>codepage</var>.
</p>
<p>The numbers in the vector <var>native_bytes</var> are rounded and clipped to
integers between 0 and 255. This byte stream is then mapped into the
code page given by the string <var>codepage</var> and returned in the string
<var>utf8_str</var>. Octave uses UTF-8 as its internal encoding. The string
<var>codepage</var> must be an identifier of a valid code page. Examples for
valid code pages are <code>"ISO-8859-1"</code>, <code>"Shift-JIS"</code>, or
<code>"UTF-16"</code>. For a list of supported code pages, see
<a href="https://www.gnu.org/software/libiconv">https://www.gnu.org/software/libiconv</a>. If <var>codepage</var> is omitted
or empty, the system default codepage is used.
</p>
<p>If <var>native_bytes</var> is a string vector, it is returned as is.
</p>
<p><strong>See also:</strong> <a href="#XREFunicode2native">unicode2native</a>.
</p></dd></dl>
<a name="XREFdo_005fstring_005fescapes"></a><dl>
<dt><a name="index-do_005fstring_005fescapes"></a><em></em> <strong>do_string_escapes</strong> <em>(<var>string</var>)</em></dt>
<dd><p>Convert escape sequences in <var>string</var> to the characters they represent.
</p>
<p>Escape sequences begin with a leading backslash
(<code>'\'</code>) followed by 1–3 characters
(.e.g., <code>"\n"</code> => newline).
</p>
<p><strong>See also:</strong> <a href="#XREFundo_005fstring_005fescapes">undo_string_escapes</a>.
</p></dd></dl>
<a name="XREFundo_005fstring_005fescapes"></a><dl>
<dt><a name="index-undo_005fstring_005fescapes"></a><em></em> <strong>undo_string_escapes</strong> <em>(<var>s</var>)</em></dt>
<dd><p>Convert special characters in strings back to their escaped forms.
</p>
<p>For example, the expression
</p>
<div class="example">
<pre class="example">bell = "\a";
</pre></div>
<p>assigns the value of the alert character (control-g, ASCII code 7) to the
string variable <code>bell</code>. If this string is printed, the system will
ring the terminal bell (if it is possible). This is normally the desired
outcome. However, sometimes it is useful to be able to print the original
representation of the string, with the special characters replaced by their
escape sequences. For example,
</p>
<div class="example">
<pre class="example">octave:13> undo_string_escapes (bell)
ans = \a
</pre></div>
<p>replaces the unprintable alert character with its printable representation.
</p>
<p><strong>See also:</strong> <a href="#XREFdo_005fstring_005fescapes">do_string_escapes</a>.
</p></dd></dl>
<hr>
<div class="header">
<p>
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