std::gamma_distribution

 

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std::gamma_distribution

Member functions

gamma_distribution::gamma_distribution

gamma_distribution::reset

Generation

gamma_distribution::operator()

Characteristics

gamma_distribution::alphagamma_distribution::beta

gamma_distribution::param

gamma_distribution::min

gamma_distribution::max

Non-member functions

operator==operator!=

operator<<operator>>

 

Defined in header <random>
template< class RealType = double > class gamma_distribution;		(since C++11)

Produces random positive floating-point values x, distributed according to probability density function:

\(\mathsf{p}(x\mid\alpha,\beta) = \frac{e^{-x/\beta} }{\beta^\alpha\cdot\Gamma(\alpha)}\cdot x^{\alpha-1} \)P(x|α,β) =

e-x/β

βα · Γ(α)

· xα-1

where α is known as the shape parameter and β is known as the scale parameter. The shape parameter is sometimes denoted by the letter k and the scale parameter is sometimes denoted by the letter θ.

For floating-point α, the value obtained is the sum of α independent exponentially distributed random variables, each of which has a mean of β

std::gamma_distribution satisfies RandomNumberDistribution

Template parameters

RealType

-

The result type generated by the generator. The effect is undefined if this is not one of float, double, or long double.

Member types

Member type	Definition
result_type	RealType
param_type	the type of the parameter set, see RandomNumberDistribution.

Member functions

(constructor)	constructs new distribution (public member function)
reset	resets the internal state of the distribution (public member function)
Generation
operator()	generates the next random number in the distribution (public member function)
Characteristics
alphabeta	returns the distribution parameters (public member function)
param	gets or sets the distribution parameter object (public member function)
min	returns the minimum potentially generated value (public member function)
max	returns the maximum potentially generated value (public member function)

Non-member functions

operator==operator!=	compares two distribution objects (function)
operator<<operator>>	performs stream input and output on pseudo-random number distribution (function template)

External links

Weisstein, Eric W. "Gamma Distribution." From MathWorld--A Wolfram Web Resource.