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26 <div class="titlepage"><div><div><h3 class="title">
27 <a name="math_toolkit.sf_beta.ibeta_function"></a><a class="link" href="ibeta_function.html" title="Incomplete Beta Functions">Incomplete Beta
29 </h3></div></div></div>
31 <a name="math_toolkit.sf_beta.ibeta_function.h0"></a>
32 <span class="phrase"><a name="math_toolkit.sf_beta.ibeta_function.synopsis"></a></span><a class="link" href="ibeta_function.html#math_toolkit.sf_beta.ibeta_function.synopsis">Synopsis</a>
34 <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">math</span><span class="special">/</span><span class="identifier">special_functions</span><span class="special">/</span><span class="identifier">beta</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
36 <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">math</span><span class="special">{</span>
38 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T2</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T3</span><span class="special">></span>
39 <a class="link" href="../result_type.html" title="Calculation of the Type of the Result"><span class="emphasis"><em>calculated-result-type</em></span></a> <span class="identifier">ibeta</span><span class="special">(</span><span class="identifier">T1</span> <span class="identifier">a</span><span class="special">,</span> <span class="identifier">T2</span> <span class="identifier">b</span><span class="special">,</span> <span class="identifier">T3</span> <span class="identifier">x</span><span class="special">);</span>
41 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T2</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T3</span><span class="special">,</span> <span class="keyword">class</span> <a class="link" href="../../policy.html" title="Chapter 20. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">></span>
42 <a class="link" href="../result_type.html" title="Calculation of the Type of the Result"><span class="emphasis"><em>calculated-result-type</em></span></a> <span class="identifier">ibeta</span><span class="special">(</span><span class="identifier">T1</span> <span class="identifier">a</span><span class="special">,</span> <span class="identifier">T2</span> <span class="identifier">b</span><span class="special">,</span> <span class="identifier">T3</span> <span class="identifier">x</span><span class="special">,</span> <span class="keyword">const</span> <a class="link" href="../../policy.html" title="Chapter 20. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">&);</span>
44 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T2</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T3</span><span class="special">></span>
45 <a class="link" href="../result_type.html" title="Calculation of the Type of the Result"><span class="emphasis"><em>calculated-result-type</em></span></a> <span class="identifier">ibetac</span><span class="special">(</span><span class="identifier">T1</span> <span class="identifier">a</span><span class="special">,</span> <span class="identifier">T2</span> <span class="identifier">b</span><span class="special">,</span> <span class="identifier">T3</span> <span class="identifier">x</span><span class="special">);</span>
47 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T2</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T3</span><span class="special">,</span> <span class="keyword">class</span> <a class="link" href="../../policy.html" title="Chapter 20. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">></span>
48 <a class="link" href="../result_type.html" title="Calculation of the Type of the Result"><span class="emphasis"><em>calculated-result-type</em></span></a> <span class="identifier">ibetac</span><span class="special">(</span><span class="identifier">T1</span> <span class="identifier">a</span><span class="special">,</span> <span class="identifier">T2</span> <span class="identifier">b</span><span class="special">,</span> <span class="identifier">T3</span> <span class="identifier">x</span><span class="special">,</span> <span class="keyword">const</span> <a class="link" href="../../policy.html" title="Chapter 20. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">&);</span>
50 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T2</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T3</span><span class="special">></span>
51 <a class="link" href="../result_type.html" title="Calculation of the Type of the Result"><span class="emphasis"><em>calculated-result-type</em></span></a> <span class="identifier">beta</span><span class="special">(</span><span class="identifier">T1</span> <span class="identifier">a</span><span class="special">,</span> <span class="identifier">T2</span> <span class="identifier">b</span><span class="special">,</span> <span class="identifier">T3</span> <span class="identifier">x</span><span class="special">);</span>
53 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T2</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T3</span><span class="special">,</span> <span class="keyword">class</span> <a class="link" href="../../policy.html" title="Chapter 20. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">></span>
54 <a class="link" href="../result_type.html" title="Calculation of the Type of the Result"><span class="emphasis"><em>calculated-result-type</em></span></a> <span class="identifier">beta</span><span class="special">(</span><span class="identifier">T1</span> <span class="identifier">a</span><span class="special">,</span> <span class="identifier">T2</span> <span class="identifier">b</span><span class="special">,</span> <span class="identifier">T3</span> <span class="identifier">x</span><span class="special">,</span> <span class="keyword">const</span> <a class="link" href="../../policy.html" title="Chapter 20. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">&);</span>
56 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T2</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T3</span><span class="special">></span>
57 <a class="link" href="../result_type.html" title="Calculation of the Type of the Result"><span class="emphasis"><em>calculated-result-type</em></span></a> <span class="identifier">betac</span><span class="special">(</span><span class="identifier">T1</span> <span class="identifier">a</span><span class="special">,</span> <span class="identifier">T2</span> <span class="identifier">b</span><span class="special">,</span> <span class="identifier">T3</span> <span class="identifier">x</span><span class="special">);</span>
59 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T2</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T3</span><span class="special">,</span> <span class="keyword">class</span> <a class="link" href="../../policy.html" title="Chapter 20. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">></span>
60 <a class="link" href="../result_type.html" title="Calculation of the Type of the Result"><span class="emphasis"><em>calculated-result-type</em></span></a> <span class="identifier">betac</span><span class="special">(</span><span class="identifier">T1</span> <span class="identifier">a</span><span class="special">,</span> <span class="identifier">T2</span> <span class="identifier">b</span><span class="special">,</span> <span class="identifier">T3</span> <span class="identifier">x</span><span class="special">,</span> <span class="keyword">const</span> <a class="link" href="../../policy.html" title="Chapter 20. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">&);</span>
62 <span class="special">}}</span> <span class="comment">// namespaces</span>
65 <a name="math_toolkit.sf_beta.ibeta_function.h1"></a>
66 <span class="phrase"><a name="math_toolkit.sf_beta.ibeta_function.description"></a></span><a class="link" href="ibeta_function.html#math_toolkit.sf_beta.ibeta_function.description">Description</a>
69 There are four <a href="http://en.wikipedia.org/wiki/Incomplete_beta_function" target="_top">incomplete
70 beta functions</a> : two are normalised versions (also known as <span class="emphasis"><em>regularized</em></span>
71 beta functions) that return values in the range [0, 1], and two are non-normalised
72 and return values in the range [0, <a class="link" href="beta_function.html" title="Beta">beta</a>(a,
73 b)]. Users interested in statistical applications should use the normalised
74 (or <a href="http://mathworld.wolfram.com/RegularizedBetaFunction.html" target="_top">regularized</a>
75 ) versions (ibeta and ibetac).
78 All of these functions require <span class="emphasis"><em>0 <= x <= 1</em></span>.
81 The normalized functions <a class="link" href="ibeta_function.html" title="Incomplete Beta Functions">ibeta</a>
82 and <a class="link" href="ibeta_function.html" title="Incomplete Beta Functions">ibetac</a> require
83 <span class="emphasis"><em>a,b >= 0</em></span>, and in addition that not both <span class="emphasis"><em>a</em></span>
84 and <span class="emphasis"><em>b</em></span> are zero.
87 The functions <a class="link" href="beta_function.html" title="Beta">beta</a>
88 and <a class="link" href="ibeta_function.html" title="Incomplete Beta Functions">betac</a> require
89 <span class="emphasis"><em>a,b > 0</em></span>.
92 The return type of these functions is computed using the <a class="link" href="../result_type.html" title="Calculation of the Type of the Result"><span class="emphasis"><em>result
93 type calculation rules</em></span></a> when T1, T2 and T3 are different
97 The final <a class="link" href="../../policy.html" title="Chapter 20. Policies: Controlling Precision, Error Handling etc">Policy</a> argument is optional and can
98 be used to control the behaviour of the function: how it handles errors,
99 what level of precision to use etc. Refer to the <a class="link" href="../../policy.html" title="Chapter 20. Policies: Controlling Precision, Error Handling etc">policy
100 documentation for more details</a>.
102 <pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T2</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T3</span><span class="special">></span>
103 <a class="link" href="../result_type.html" title="Calculation of the Type of the Result"><span class="emphasis"><em>calculated-result-type</em></span></a> <span class="identifier">ibeta</span><span class="special">(</span><span class="identifier">T1</span> <span class="identifier">a</span><span class="special">,</span> <span class="identifier">T2</span> <span class="identifier">b</span><span class="special">,</span> <span class="identifier">T3</span> <span class="identifier">x</span><span class="special">);</span>
105 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T2</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T3</span><span class="special">,</span> <span class="keyword">class</span> <a class="link" href="../../policy.html" title="Chapter 20. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">></span>
106 <a class="link" href="../result_type.html" title="Calculation of the Type of the Result"><span class="emphasis"><em>calculated-result-type</em></span></a> <span class="identifier">ibeta</span><span class="special">(</span><span class="identifier">T1</span> <span class="identifier">a</span><span class="special">,</span> <span class="identifier">T2</span> <span class="identifier">b</span><span class="special">,</span> <span class="identifier">T3</span> <span class="identifier">x</span><span class="special">,</span> <span class="keyword">const</span> <a class="link" href="../../policy.html" title="Chapter 20. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">&);</span>
109 Returns the normalised incomplete beta function of a, b and x:
111 <div class="blockquote"><blockquote class="blockquote"><p>
112 <span class="inlinemediaobject"><img src="../../../equations/ibeta3.svg"></span>
114 </p></blockquote></div>
115 <div class="blockquote"><blockquote class="blockquote"><p>
116 <span class="inlinemediaobject"><img src="../../../graphs/ibeta.svg" align="middle"></span>
118 </p></blockquote></div>
119 <pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T2</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T3</span><span class="special">></span>
120 <a class="link" href="../result_type.html" title="Calculation of the Type of the Result"><span class="emphasis"><em>calculated-result-type</em></span></a> <span class="identifier">ibetac</span><span class="special">(</span><span class="identifier">T1</span> <span class="identifier">a</span><span class="special">,</span> <span class="identifier">T2</span> <span class="identifier">b</span><span class="special">,</span> <span class="identifier">T3</span> <span class="identifier">x</span><span class="special">);</span>
122 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T2</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T3</span><span class="special">,</span> <span class="keyword">class</span> <a class="link" href="../../policy.html" title="Chapter 20. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">></span>
123 <a class="link" href="../result_type.html" title="Calculation of the Type of the Result"><span class="emphasis"><em>calculated-result-type</em></span></a> <span class="identifier">ibetac</span><span class="special">(</span><span class="identifier">T1</span> <span class="identifier">a</span><span class="special">,</span> <span class="identifier">T2</span> <span class="identifier">b</span><span class="special">,</span> <span class="identifier">T3</span> <span class="identifier">x</span><span class="special">,</span> <span class="keyword">const</span> <a class="link" href="../../policy.html" title="Chapter 20. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">&);</span>
126 Returns the normalised complement of the incomplete beta function of a, b
129 <div class="blockquote"><blockquote class="blockquote"><p>
130 <span class="inlinemediaobject"><img src="../../../equations/ibeta4.svg"></span>
132 </p></blockquote></div>
133 <pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T2</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T3</span><span class="special">></span>
134 <a class="link" href="../result_type.html" title="Calculation of the Type of the Result"><span class="emphasis"><em>calculated-result-type</em></span></a> <span class="identifier">beta</span><span class="special">(</span><span class="identifier">T1</span> <span class="identifier">a</span><span class="special">,</span> <span class="identifier">T2</span> <span class="identifier">b</span><span class="special">,</span> <span class="identifier">T3</span> <span class="identifier">x</span><span class="special">);</span>
136 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T2</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T3</span><span class="special">,</span> <span class="keyword">class</span> <a class="link" href="../../policy.html" title="Chapter 20. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">></span>
137 <a class="link" href="../result_type.html" title="Calculation of the Type of the Result"><span class="emphasis"><em>calculated-result-type</em></span></a> <span class="identifier">beta</span><span class="special">(</span><span class="identifier">T1</span> <span class="identifier">a</span><span class="special">,</span> <span class="identifier">T2</span> <span class="identifier">b</span><span class="special">,</span> <span class="identifier">T3</span> <span class="identifier">x</span><span class="special">,</span> <span class="keyword">const</span> <a class="link" href="../../policy.html" title="Chapter 20. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">&);</span>
140 Returns the full (non-normalised) incomplete beta function of a, b and x:
142 <div class="blockquote"><blockquote class="blockquote"><p>
143 <span class="inlinemediaobject"><img src="../../../equations/ibeta1.svg"></span>
145 </p></blockquote></div>
146 <pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T2</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T3</span><span class="special">></span>
147 <a class="link" href="../result_type.html" title="Calculation of the Type of the Result"><span class="emphasis"><em>calculated-result-type</em></span></a> <span class="identifier">betac</span><span class="special">(</span><span class="identifier">T1</span> <span class="identifier">a</span><span class="special">,</span> <span class="identifier">T2</span> <span class="identifier">b</span><span class="special">,</span> <span class="identifier">T3</span> <span class="identifier">x</span><span class="special">);</span>
149 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T1</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T2</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T3</span><span class="special">,</span> <span class="keyword">class</span> <a class="link" href="../../policy.html" title="Chapter 20. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">></span>
150 <a class="link" href="../result_type.html" title="Calculation of the Type of the Result"><span class="emphasis"><em>calculated-result-type</em></span></a> <span class="identifier">betac</span><span class="special">(</span><span class="identifier">T1</span> <span class="identifier">a</span><span class="special">,</span> <span class="identifier">T2</span> <span class="identifier">b</span><span class="special">,</span> <span class="identifier">T3</span> <span class="identifier">x</span><span class="special">,</span> <span class="keyword">const</span> <a class="link" href="../../policy.html" title="Chapter 20. Policies: Controlling Precision, Error Handling etc">Policy</a><span class="special">&);</span>
153 Returns the full (non-normalised) complement of the incomplete beta function
156 <div class="blockquote"><blockquote class="blockquote"><p>
157 <span class="inlinemediaobject"><img src="../../../equations/ibeta2.svg"></span>
159 </p></blockquote></div>
161 <a name="math_toolkit.sf_beta.ibeta_function.h2"></a>
162 <span class="phrase"><a name="math_toolkit.sf_beta.ibeta_function.accuracy"></a></span><a class="link" href="ibeta_function.html#math_toolkit.sf_beta.ibeta_function.accuracy">Accuracy</a>
165 The following tables give peak and mean relative errors in over various domains
166 of a, b and x, along with comparisons to the <a href="http://www.gnu.org/software/gsl/" target="_top">GSL-1.9</a>
167 and <a href="http://www.netlib.org/cephes/" target="_top">Cephes</a> libraries.
168 Note that only results for the widest floating-point type on the system are
169 given as narrower types have <a class="link" href="../relative_error.html#math_toolkit.relative_error.zero_error">effectively
173 Note that the results for 80 and 128-bit long doubles are noticeably higher
174 than for doubles: this is because the wider exponent range of these types
175 allow more extreme test cases to be tested. For example expected results
176 that are zero at double precision, may be finite but exceptionally small
177 with the wider exponent range of the long double types.
180 <a name="math_toolkit.sf_beta.ibeta_function.table_ibeta"></a><p class="title"><b>Table 8.18. Error rates for ibeta</b></p>
181 <div class="table-contents"><table class="table" summary="Error rates for ibeta">
194 GNU C++ version 7.1.0<br> linux<br> double
199 GNU C++ version 7.1.0<br> linux<br> long double
204 Sun compiler version 0x5150<br> Sun Solaris<br> long double
209 Microsoft Visual C++ version 14.1<br> Win32<br> double
217 Incomplete Beta Function: Small Values
222 <span class="blue">Max = 0ε (Mean = 0ε)</span><br> <br> (<span class="emphasis"><em>GSL
223 2.1:</em></span> Max = 682ε (Mean = 32.6ε))<br> (<span class="emphasis"><em>Rmath
224 3.2.3:</em></span> Max = 22.9ε (Mean = 3.35ε))
229 <span class="blue">Max = 8.97ε (Mean = 2.09ε)</span>
234 <span class="blue">Max = 21.3ε (Mean = 2.75ε)</span>
239 <span class="blue">Max = 8.4ε (Mean = 1.93ε)</span>
246 Incomplete Beta Function: Medium Values
251 <span class="blue">Max = 0ε (Mean = 0ε)</span><br> <br> (<span class="emphasis"><em>GSL
252 2.1:</em></span> Max = 690ε (Mean = 151ε))<br> (<span class="emphasis"><em>Rmath 3.2.3:</em></span>
253 Max = 232ε (Mean = 27.9ε))
258 <span class="blue">Max = 50ε (Mean = 12.1ε)</span>
263 <span class="blue">Max = 124ε (Mean = 18.4ε)</span>
268 <span class="blue">Max = 106ε (Mean = 16.3ε)</span>
275 Incomplete Beta Function: Large and Diverse Values
280 <span class="blue">Max = 1.26ε (Mean = 0.063ε)</span><br> <br>
281 (<span class="emphasis"><em>GSL 2.1:</em></span> Max = 3.9e+05ε (Mean = 1.82e+04ε)
282 <a class="link" href="../logs_and_tables/logs.html#errors_GNU_C_version_7_1_0_linux_double_ibeta_GSL_2_1_Incomplete_Beta_Function_Large_and_Diverse_Values">And
283 other failures.</a>)<br> (<span class="emphasis"><em>Rmath 3.2.3:</em></span>
284 Max = 574ε (Mean = 49.4ε))
289 <span class="blue">Max = 1.96e+04ε (Mean = 997ε)</span>
294 <span class="blue">Max = 4.98e+04ε (Mean = 2.07e+03ε)</span>
299 <span class="blue">Max = 1.32e+03ε (Mean = 68.5ε)</span>
306 Incomplete Beta Function: Small Integer Values
311 <span class="blue">Max = 0ε (Mean = 0ε)</span><br> <br> (<span class="emphasis"><em>GSL
312 2.1:</em></span> Max = 254ε (Mean = 50.9ε))<br> (<span class="emphasis"><em>Rmath
313 3.2.3:</em></span> Max = 62.2ε (Mean = 8.95ε))
318 <span class="blue">Max = 4.45ε (Mean = 0.814ε)</span>
323 <span class="blue">Max = 44.5ε (Mean = 10.1ε)</span>
328 <span class="blue">Max = 3.85ε (Mean = 0.791ε)</span>
335 <br class="table-break"><div class="table">
336 <a name="math_toolkit.sf_beta.ibeta_function.table_ibetac"></a><p class="title"><b>Table 8.19. Error rates for ibetac</b></p>
337 <div class="table-contents"><table class="table" summary="Error rates for ibetac">
350 GNU C++ version 7.1.0<br> linux<br> double
355 GNU C++ version 7.1.0<br> linux<br> long double
360 Sun compiler version 0x5150<br> Sun Solaris<br> long double
365 Microsoft Visual C++ version 14.1<br> Win32<br> double
373 Incomplete Beta Function: Small Values
378 <span class="blue">Max = 0ε (Mean = 0ε)</span><br> <br> (<span class="emphasis"><em>Rmath
379 3.2.3:</em></span> Max = 22.4ε (Mean = 3.67ε))
384 <span class="blue">Max = 10.6ε (Mean = 2.22ε)</span>
389 <span class="blue">Max = 13.8ε (Mean = 2.68ε)</span>
394 <span class="blue">Max = 6.94ε (Mean = 1.71ε)</span>
401 Incomplete Beta Function: Medium Values
406 <span class="blue">Max = 0ε (Mean = 0ε)</span><br> <br> (<span class="emphasis"><em>Rmath
407 3.2.3:</em></span> Max = 204ε (Mean = 25.8ε))
412 <span class="blue">Max = 73.9ε (Mean = 11.2ε)</span>
417 <span class="blue">Max = 132ε (Mean = 19.8ε)</span>
422 <span class="blue">Max = 56.7ε (Mean = 14.3ε)</span>
429 Incomplete Beta Function: Large and Diverse Values
434 <span class="blue">Max = 0.981ε (Mean = 0.0573ε)</span><br>
435 <br> (<span class="emphasis"><em>Rmath 3.2.3:</em></span> Max = 889ε (Mean = 68.4ε))
440 <span class="blue">Max = 3.45e+04ε (Mean = 1.32e+03ε)</span>
445 <span class="blue">Max = 6.31e+04ε (Mean = 2.04e+03ε)</span>
450 <span class="blue">Max = 1.88e+03ε (Mean = 82.7ε)</span>
457 Incomplete Beta Function: Small Integer Values
462 <span class="blue">Max = 0ε (Mean = 0ε)</span><br> <br> (<span class="emphasis"><em>Rmath
463 3.2.3:</em></span> Max = 84.6ε (Mean = 18ε))
468 <span class="blue">Max = 5.34ε (Mean = 1.11ε)</span>
473 <span class="blue">Max = 107ε (Mean = 17.1ε)</span>
478 <span class="blue">Max = 6.37ε (Mean = 1.03ε)</span>
485 <br class="table-break"><div class="table">
486 <a name="math_toolkit.sf_beta.ibeta_function.table_beta_incomplete_"></a><p class="title"><b>Table 8.20. Error rates for beta (incomplete)</b></p>
487 <div class="table-contents"><table class="table" summary="Error rates for beta (incomplete)">
500 GNU C++ version 7.1.0<br> linux<br> double
505 GNU C++ version 7.1.0<br> linux<br> long double
510 Sun compiler version 0x5150<br> Sun Solaris<br> long double
515 Microsoft Visual C++ version 14.1<br> Win32<br> double
523 Incomplete Beta Function: Small Values
528 <span class="blue">Max = 0ε (Mean = 0ε)</span>
533 <span class="blue">Max = 11.1ε (Mean = 2.32ε)</span>
538 <span class="blue">Max = 18.7ε (Mean = 3.19ε)</span>
543 <span class="blue">Max = 9.94ε (Mean = 2.17ε)</span>
550 Incomplete Beta Function: Medium Values
555 <span class="blue">Max = 0.568ε (Mean = 0.0254ε)</span>
560 <span class="blue">Max = 69.2ε (Mean = 13.4ε)</span>
565 <span class="blue">Max = 174ε (Mean = 25ε)</span>
570 <span class="blue">Max = 90ε (Mean = 12.7ε)</span>
577 Incomplete Beta Function: Large and Diverse Values
582 <span class="blue">Max = 0.999ε (Mean = 0.0325ε)</span>
587 <span class="blue">Max = 6.84e+04ε (Mean = 2.76e+03ε)</span>
592 <span class="blue">Max = 6.86e+04ε (Mean = 2.79e+03ε)</span>
597 <span class="blue">Max = 633ε (Mean = 29.7ε)</span>
604 Incomplete Beta Function: Small Integer Values
609 <span class="blue">Max = 0.786ε (Mean = 0.0323ε)</span>
614 <span class="blue">Max = 11.6ε (Mean = 3.6ε)</span>
619 <span class="blue">Max = 51.8ε (Mean = 11ε)</span>
624 <span class="blue">Max = 26ε (Mean = 6.28ε)</span>
631 <br class="table-break"><div class="table">
632 <a name="math_toolkit.sf_beta.ibeta_function.table_betac"></a><p class="title"><b>Table 8.21. Error rates for betac</b></p>
633 <div class="table-contents"><table class="table" summary="Error rates for betac">
646 GNU C++ version 7.1.0<br> linux<br> double
651 GNU C++ version 7.1.0<br> linux<br> long double
656 Sun compiler version 0x5150<br> Sun Solaris<br> long double
661 Microsoft Visual C++ version 14.1<br> Win32<br> double
669 Incomplete Beta Function: Small Values
674 <span class="blue">Max = 0.676ε (Mean = 0.0302ε)</span>
679 <span class="blue">Max = 9.92ε (Mean = 2.3ε)</span>
684 <span class="blue">Max = 11.2ε (Mean = 2.94ε)</span>
689 <span class="blue">Max = 8.94ε (Mean = 2.06ε)</span>
696 Incomplete Beta Function: Medium Values
701 <span class="blue">Max = 0.949ε (Mean = 0.098ε)</span>
706 <span class="blue">Max = 63.5ε (Mean = 13.5ε)</span>
711 <span class="blue">Max = 97.6ε (Mean = 24.3ε)</span>
716 <span class="blue">Max = 90.6ε (Mean = 14.8ε)</span>
723 Incomplete Beta Function: Large and Diverse Values
728 <span class="blue">Max = 1.12ε (Mean = 0.0458ε)</span>
733 <span class="blue">Max = 1.05e+05ε (Mean = 5.45e+03ε)</span>
738 <span class="blue">Max = 1.04e+05ε (Mean = 5.46e+03ε)</span>
743 <span class="blue">Max = 3.72e+03ε (Mean = 113ε)</span>
750 Incomplete Beta Function: Small Integer Values
755 <span class="blue">Max = 0.586ε (Mean = 0.0314ε)</span>
760 <span class="blue">Max = 11.1ε (Mean = 3.65ε)</span>
765 <span class="blue">Max = 103ε (Mean = 17.4ε)</span>
770 <span class="blue">Max = 26.2ε (Mean = 6.36ε)</span>
777 <br class="table-break"><h5>
778 <a name="math_toolkit.sf_beta.ibeta_function.h3"></a>
779 <span class="phrase"><a name="math_toolkit.sf_beta.ibeta_function.testing"></a></span><a class="link" href="ibeta_function.html#math_toolkit.sf_beta.ibeta_function.testing">Testing</a>
782 There are two sets of tests: spot tests compare values taken from <a href="http://functions.wolfram.com/webMathematica/FunctionEvaluation.jsp?name=BetaRegularized" target="_top">Mathworld's
783 online function evaluator</a> with this implementation: they provide
784 a basic "sanity check" for the implementation, with one spot-test
785 in each implementation-domain (see implementation notes below).
788 Accuracy tests use data generated at very high precision (with <a href="http://shoup.net/ntl/doc/RR.txt" target="_top">NTL
789 RR class</a> set at 1000-bit precision), using the "textbook"
790 continued fraction representation (refer to the first continued fraction
791 in the implementation discussion below). Note that this continued fraction
792 is <span class="emphasis"><em>not</em></span> used in the implementation, and therefore we
793 have test data that is fully independent of the code.
796 <a name="math_toolkit.sf_beta.ibeta_function.h4"></a>
797 <span class="phrase"><a name="math_toolkit.sf_beta.ibeta_function.implementation"></a></span><a class="link" href="ibeta_function.html#math_toolkit.sf_beta.ibeta_function.implementation">Implementation</a>
800 This implementation is closely based upon <a href="http://portal.acm.org/citation.cfm?doid=131766.131776" target="_top">"Algorithm
801 708; Significant digit computation of the incomplete beta function ratios",
802 DiDonato and Morris, ACM, 1992.</a>
805 All four of these functions share a common implementation: this is passed
806 both x and y, and can return either p or q where these are related by:
808 <div class="blockquote"><blockquote class="blockquote"><p>
809 <span class="inlinemediaobject"><img src="../../../equations/ibeta_inv5.svg"></span>
811 </p></blockquote></div>
813 so at any point we can swap a for b, x for y and p for q if this results
814 in a more favourable position. Generally such swaps are performed so that
815 we always compute a value less than 0.9: when required this can then be subtracted
816 from 1 without undue cancellation error.
819 The following continued fraction representation is found in many textbooks
820 but is not used in this implementation - it's both slower and less accurate
821 than the alternatives - however it is used to generate test data:
823 <div class="blockquote"><blockquote class="blockquote"><p>
824 <span class="inlinemediaobject"><img src="../../../equations/ibeta5.svg"></span>
826 </p></blockquote></div>
828 The following continued fraction is due to <a href="http://portal.acm.org/citation.cfm?doid=131766.131776" target="_top">Didonato
829 and Morris</a>, and is used in this implementation when a and b are both
832 <div class="blockquote"><blockquote class="blockquote"><p>
833 <span class="inlinemediaobject"><img src="../../../equations/ibeta6.svg"></span>
835 </p></blockquote></div>
837 For smallish b and x then a series representation can be used:
839 <div class="blockquote"><blockquote class="blockquote"><p>
840 <span class="inlinemediaobject"><img src="../../../equations/ibeta7.svg"></span>
842 </p></blockquote></div>
844 When b << a then the transition from 0 to 1 occurs very close to x
845 = 1 and some care has to be taken over the method of computation, in that
846 case the following series representation is used:
848 <div class="blockquote"><blockquote class="blockquote"><p>
849 <span class="inlinemediaobject"><img src="../../../equations/ibeta8.svg"></span>
851 </p></blockquote></div>
853 Where Q(a,x) is an <a href="http://functions.wolfram.com/GammaBetaErf/Gamma2/" target="_top">incomplete
854 gamma function</a>. Note that this method relies on keeping a table of
855 all the p<sub>n </sub> previously computed, which does limit the precision of the method,
856 depending upon the size of the table used.
859 When <span class="emphasis"><em>a</em></span> and <span class="emphasis"><em>b</em></span> are both small integers,
860 then we can relate the incomplete beta to the binomial distribution and use
861 the following finite sum:
863 <div class="blockquote"><blockquote class="blockquote"><p>
864 <span class="inlinemediaobject"><img src="../../../equations/ibeta12.svg"></span>
866 </p></blockquote></div>
868 Finally we can sidestep difficult areas, or move to an area with a more efficient
869 means of computation, by using the duplication formulae:
871 <div class="blockquote"><blockquote class="blockquote"><p>
872 <span class="inlinemediaobject"><img src="../../../equations/ibeta10.svg"></span>
874 </p></blockquote></div>
875 <div class="blockquote"><blockquote class="blockquote"><p>
876 <span class="inlinemediaobject"><img src="../../../equations/ibeta11.svg"></span>
878 </p></blockquote></div>
880 The domains of a, b and x for which the various methods are used are identical
881 to those described in the <a href="http://portal.acm.org/citation.cfm?doid=131766.131776" target="_top">Didonato
882 and Morris TOMS 708 paper</a>.
885 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
886 <td align="left"></td>
887 <td align="right"><div class="copyright-footer">Copyright © 2006-2019 Nikhar
888 Agrawal, Anton Bikineev, Paul A. Bristow, Marco Guazzone, Christopher Kormanyos,
889 Hubert Holin, Bruno Lalande, John Maddock, Jeremy Murphy, Matthew Pulver, Johan
890 Råde, Gautam Sewani, Benjamin Sobotta, Nicholas Thompson, Thijs van den Berg,
891 Daryle Walker and Xiaogang Zhang<p>
892 Distributed under the Boost Software License, Version 1.0. (See accompanying
893 file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
898 <div class="spirit-nav">
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