##### cppreference.com

##### Search

Create account

##### Namespaces

- Page
- Discussion

##### Variants

##### Views

- View
- Edit
- History

##### Actions

# std::gamma_distribution

From cppreference.com
< cpp‎ | numeric‎ | random

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:

  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`

### [edit] 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.

### [edit] Member types

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

### [edit] Member functions

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

### [edit] Non-member functions

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

### [edit] Example

| This section is incomplete Reason: no example

### [edit] External links

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

Retrieved from "http://en.cppreference.com/mwiki/index.php?title=cpp/numeric/random/gamma_distribution&oldid=85842"
Category:

- Todo no example