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101 lines
3.9 KiB
HTML
101 lines
3.9 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>erf (LIBM)</title>
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<meta name="description" content="erf (LIBM)">
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<meta name="keywords" content="erf (LIBM)">
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<link href="Document-Index.html#Document-Index" rel="index" title="Document Index">
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<link href="Document-Index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Math.html#Math" rel="up" title="Math">
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<link href="exp.html#exp" rel="next" title="exp">
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<link href="cosh.html#cosh" rel="prev" title="cosh">
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<body lang="en">
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<a name="erf"></a>
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<div class="header">
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<p>
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Next: <a href="exp.html#exp" accesskey="n" rel="next">exp</a>, Previous: <a href="cosh.html#cosh" accesskey="p" rel="prev">cosh</a>, Up: <a href="Math.html#Math" accesskey="u" rel="up">Math</a> [<a href="Document-Index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Document-Index.html#Document-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="erf_002c-erff_002c-erfc_002c-erfcf_002d_002d_002derror-function"></a>
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<h3 class="section">1.14 <code>erf</code>, <code>erff</code>, <code>erfc</code>, <code>erfcf</code>—error function</h3>
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<a name="index-erf"></a>
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<a name="index-erff"></a>
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<a name="index-erfc"></a>
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<a name="index-erfcf"></a>
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<p><strong>Synopsis</strong>
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</p><div class="example">
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<pre class="example">#include <math.h>
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double erf(double <var>x</var>);
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float erff(float <var>x</var>);
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double erfc(double <var>x</var>);
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float erfcf(float <var>x</var>);
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</pre></div>
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<p><strong>Description</strong><br>
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<code>erf</code> calculates an approximation to the “error function”,
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which estimates the probability that an observation will fall within
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<var>x</var> standard deviations of the mean (assuming a normal
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distribution).
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</p>
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<p><code>erfc</code> calculates the complementary probability; that is,
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<code>erfc(<var>x</var>)</code> is <code>1 - erf(<var>x</var>)</code>. <code>erfc</code> is computed directly,
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so that you can use it to avoid the loss of precision that would
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result from subtracting large probabilities (on large <var>x</var>) from 1.
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</p>
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<p><code>erff</code> and <code>erfcf</code> differ from <code>erf</code> and <code>erfc</code> only in the
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argument and result types.
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</p>
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<br>
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<p><strong>Returns</strong><br>
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For positive arguments, <code>erf</code> and all its variants return a
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probability—a number between 0 and 1.
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</p>
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<br>
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<p><strong>Portability</strong><br>
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None of the variants of <code>erf</code> are ANSI C.
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</p>
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<br>
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</body>
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</html>
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