std::gamma_distribution< _RealType > Class Template Reference
[Continuous Distributions]

A gamma continuous distribution for random numbers. More...

List of all members.

Public Types

• typedef _RealType input_type
• typedef _RealType result_type

Public Member Functions

• _RealType alpha () const
• gamma_distribution (const result_type &__alpha_val=result_type(1))
• template<class _UniformRandomNumberGenerator > result_type operator() (_UniformRandomNumberGenerator &__urng)
• void reset ()

Friends

• template<typename _RealType1 , typename _CharT , typename _Traits > std::basic_ostream< _CharT,
  _Traits > & operator<< (std::basic_ostream< _CharT, _Traits > &__os, const gamma_distribution< _RealType1 > &__x)
• template<typename _CharT , typename _Traits > std::basic_istream< _CharT,
  _Traits > & operator>> (std::basic_istream< _CharT, _Traits > &__is, gamma_distribution &__x)

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Detailed Description

template<typename _RealType = double>
class std::gamma_distribution< _RealType >

A gamma continuous distribution for random numbers.

The formula for the gamma probability mass function is .

Definition at line 2320 of file tr1_impl/random.

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Constructor & Destructor Documentation

template<typename _RealType = double>

std::gamma_distribution< _RealType >::gamma_distribution

(

const result_type &

__alpha_val = result_type(1)

)

[inline, explicit]

Constructs a gamma distribution with parameters .

Definition at line 2332 of file tr1_impl/random.

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Member Function Documentation

template<typename _RealType = double>

_RealType std::gamma_distribution< _RealType >::alpha

(

)

const [inline]

Gets the of the distribution.

Definition at line 2343 of file tr1_impl/random.

template<typename _RealType >

template<class _UniformRandomNumberGenerator >

gamma_distribution< _RealType >::result_type std::gamma_distribution< _RealType >::operator()

(

_UniformRandomNumberGenerator &

__urng

)

[inline]

Cheng's rejection algorithm GB for alpha >= 1 and a modification of Vaduva's rejection from Weibull algorithm due to Devroye for alpha < 1.

References: Cheng, R. C. "The Generation of Gamma Random Variables with Non-integral Shape Parameter." Applied Statistics, 26, 71-75, 1977.

Vaduva, I. "Computer Generation of Gamma Gandom Variables by Rejection and Composition Procedures." Math. Operationsforschung and Statistik, Series in Statistics, 8, 545-576, 1977.

Devroye, L. "Non-Uniform Random Variates Generation." Springer-Verlag, New York, 1986, Ch. IX, Sect. 3.4 (+ Errata!).

Definition at line 1501 of file random.tcc.

References std::exp(), std::log(), and std::pow().

template<typename _RealType = double>

void std::gamma_distribution< _RealType >::reset

(

)

[inline]

Resets the distribution.

Definition at line 2350 of file tr1_impl/random.

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Friends And Related Function Documentation

template<typename _RealType = double>

template<typename _RealType1 , typename _CharT , typename _Traits >

std::basic_ostream<_CharT, _Traits>& operator<<	(	std::basic_ostream< _CharT, _Traits > &	__os,
		const gamma_distribution< _RealType1 > &	__x
	)			[friend]

Inserts a gamma_distribution random number distribution __x into the output stream __os.

Parameters:

	__os	An output stream.
	__x	A gamma_distribution random number distribution.

Returns:

The output stream with the state of __x inserted or in an error state.

template<typename _RealType = double>

template<typename _CharT , typename _Traits >

std::basic_istream<_CharT, _Traits>& operator>>	(	std::basic_istream< _CharT, _Traits > &	__is,
		gamma_distribution< _RealType > &	__x
	)			[friend]

Extracts a gamma_distribution random number distribution __x from the input stream __is.

Parameters:

	__is	An input stream.
	__x	A gamma_distribution random number generator engine.

Returns:

The input stream with __x extracted or in an error state.

Definition at line 2382 of file tr1_impl/random.

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The documentation for this class was generated from the following files:

• tr1_impl/random
• random.tcc