public member function
<random>
| (1) | explicit gamma_distribution ( result_type alpha = 1.0, result_type beta = 1.0 );
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| (2) | explicit gamma_distribution ( const param_type& parm ); |
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Construct gamma distribution
Constructs a gamma_distribution object, adopting the distribution parameters specified either by alpha and beta or by object parm.
Parameters
- alpha
- Parameter alpha (α), that defines the shape of the distribution.
This shall be a positive value (α>0).
result_type is a member type that represents the type of the random numbers generated on each call to operator(). It is defined as an alias of the first class template parameter (RealType).
- beta
- Parameter beta (β), that defines the scale of the distribution.
This shall be a positive value (β>0).
result_type is a member type that represents the type of the random numbers generated on each call to operator(). It is defined as an alias of the first class template parameter (RealType).
- parm
- An object representing the distribution's parameters, obtained by a call to member function param.
param_type is a member type.
Example
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// gamma_distribution example
#include <iostream>
#include <chrono>
#include <random>
int main()
{
// construct a trivial random generator engine from a time-based seed:
unsigned seed = std::chrono::system_clock::now().time_since_epoch().count();
std::default_random_engine generator (seed);
std::gamma_distribution<double> distribution (2.0,2.0);
std::cout << "some gamma-distributed(2.0,2.0) results:" << std::endl;
for (int i=0; i<10; ++i)
std::cout << distribution(generator) << std::endl;
return 0;
}
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Possible output:
some gamma-distributed(2.0,2.0) results:
0.733997
4.04085
8.06862
3.02265
1.19829
2.32557
5.8804
8.40545
3.40881
1.04075
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