/usr/include/boost/random/chi_squared_distribution.hpp is in libboost1.49-dev 1.49.0-3.2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 | /* boost random/chi_squared_distribution.hpp header file
*
* Copyright Steven Watanabe 2011
* Distributed under the Boost Software License, Version 1.0. (See
* accompanying file LICENSE_1_0.txt or copy at
* http://www.boost.org/LICENSE_1_0.txt)
*
* See http://www.boost.org for most recent version including documentation.
*
* $Id: chi_squared_distribution.hpp 71018 2011-04-05 21:27:52Z steven_watanabe $
*/
#ifndef BOOST_RANDOM_CHI_SQUARED_DISTRIBUTION_HPP_INCLUDED
#define BOOST_RANDOM_CHI_SQUARED_DISTRIBUTION_HPP_INCLUDED
#include <iosfwd>
#include <boost/limits.hpp>
#include <boost/random/detail/config.hpp>
#include <boost/random/gamma_distribution.hpp>
namespace boost {
namespace random {
/**
* The chi squared distribution is a real valued distribution with
* one parameter, @c n. The distribution produces values > 0.
*
* The distribution function is
* \f$\displaystyle P(x) = \frac{x^{(n/2)-1}e^{-x/2}}{\Gamma(n/2)2^{n/2}}\f$.
*/
template<class RealType = double>
class chi_squared_distribution {
public:
typedef RealType result_type;
typedef RealType input_type;
class param_type {
public:
typedef chi_squared_distribution distribution_type;
/**
* Construct a param_type object. @c n
* is the parameter of the distribution.
*
* Requires: t >=0 && 0 <= p <= 1
*/
explicit param_type(RealType n_arg = RealType(1))
: _n(n_arg)
{}
/** Returns the @c n parameter of the distribution. */
RealType n() const { return _n; }
#ifndef BOOST_RANDOM_NO_STREAM_OPERATORS
/** Writes the parameters of the distribution to a @c std::ostream. */
template<class CharT, class Traits>
friend std::basic_ostream<CharT,Traits>&
operator<<(std::basic_ostream<CharT,Traits>& os,
const param_type& parm)
{
os << parm._n;
return os;
}
/** Reads the parameters of the distribution from a @c std::istream. */
template<class CharT, class Traits>
friend std::basic_istream<CharT,Traits>&
operator>>(std::basic_istream<CharT,Traits>& is, param_type& parm)
{
is >> parm._n;
return is;
}
#endif
/** Returns true if the parameters have the same values. */
friend bool operator==(const param_type& lhs, const param_type& rhs)
{
return lhs._n == rhs._n;
}
/** Returns true if the parameters have different values. */
friend bool operator!=(const param_type& lhs, const param_type& rhs)
{
return !(lhs == rhs);
}
private:
RealType _n;
};
/**
* Construct a @c chi_squared_distribution object. @c n
* is the parameter of the distribution.
*
* Requires: t >=0 && 0 <= p <= 1
*/
explicit chi_squared_distribution(RealType n_arg = RealType(1))
: _impl(n_arg / 2)
{
}
/**
* Construct an @c chi_squared_distribution object from the
* parameters.
*/
explicit chi_squared_distribution(const param_type& parm)
: _impl(parm.n() / 2)
{
}
/**
* Returns a random variate distributed according to the
* chi squared distribution.
*/
template<class URNG>
RealType operator()(URNG& urng)
{
return 2 * _impl(urng);
}
/**
* Returns a random variate distributed according to the
* chi squared distribution with parameters specified by @c param.
*/
template<class URNG>
RealType operator()(URNG& urng, const param_type& parm) const
{
return chi_squared_distribution(parm)(urng);
}
/** Returns the @c n parameter of the distribution. */
RealType n() const { return 2 * _impl.alpha(); }
/** Returns the smallest value that the distribution can produce. */
RealType min BOOST_PREVENT_MACRO_SUBSTITUTION() const { return 0; }
/** Returns the largest value that the distribution can produce. */
RealType max BOOST_PREVENT_MACRO_SUBSTITUTION() const
{ return (std::numeric_limits<RealType>::infinity)(); }
/** Returns the parameters of the distribution. */
param_type param() const { return param_type(n()); }
/** Sets parameters of the distribution. */
void param(const param_type& parm)
{
typedef gamma_distribution<RealType> impl_type;
typename impl_type::param_type impl_parm(parm.n() / 2);
_impl.param(impl_parm);
}
/**
* Effects: Subsequent uses of the distribution do not depend
* on values produced by any engine prior to invoking reset.
*/
void reset() { _impl.reset(); }
#ifndef BOOST_RANDOM_NO_STREAM_OPERATORS
/** Writes the parameters of the distribution to a @c std::ostream. */
template<class CharT, class Traits>
friend std::basic_ostream<CharT,Traits>&
operator<<(std::basic_ostream<CharT,Traits>& os,
const chi_squared_distribution& c2d)
{
os << c2d.param();
return os;
}
/** Reads the parameters of the distribution from a @c std::istream. */
template<class CharT, class Traits>
friend std::basic_istream<CharT,Traits>&
operator>>(std::basic_istream<CharT,Traits>& is,
chi_squared_distribution& c2d)
{
c2d.read(is);
return is;
}
#endif
/** Returns true if the two distributions will produce the same
sequence of values, given equal generators. */
friend bool operator==(const chi_squared_distribution& lhs,
const chi_squared_distribution& rhs)
{
return lhs._impl == rhs._impl;
}
/** Returns true if the two distributions could produce different
sequences of values, given equal generators. */
friend bool operator!=(const chi_squared_distribution& lhs,
const chi_squared_distribution& rhs)
{
return !(lhs == rhs);
}
private:
/// @cond show_private
template<class CharT, class Traits>
void read(std::basic_istream<CharT, Traits>& is) {
param_type parm;
if(is >> parm) {
param(parm);
}
}
gamma_distribution<RealType> _impl;
/// @endcond
};
}
}
#endif
|