/C++

# std::gamma_distribution

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

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

### Non-member functions

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

### Example

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