std::poisson_distribution
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poisson_distribution
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std::poisson_distribution
Member functions
Generation
Characteristics
Non-member functions
(C++11)(C++11)(until C++20)
(C++11)(C++11)
Defined in header
<random>
template< class IntType = int >
class poisson_distribution;
(since C++11)
class poisson_distribution;
Produces random non-negative integer values i, distributed according to discrete probability function:
- \(P(i | \mu) = \frac{e^{-\mu}\mu^i}{i!}\)P(i|μ) = e-μ
·μii!
The value obtained is the probability of exactly i occurrences of a random event if the expected, mean number of its occurrence under the same conditions (on the same time/space interval) is μ.
std::poisson_distribution satisfies RandomNumberDistribution.
Contents
[edit] Template parameters
IntType
-
The result type generated by the generator. The effect is undefined if this is not one of short, int, long, long long, unsigned short, unsigned int, unsigned long, or unsigned long long.
[edit] Member types
Member type
Definition
result_type (C++11)
IntType
[edit] Member functions
Generation
Characteristics
(C++11)
(public member function) [edit]
[edit] Non-member functions
(C++11)
(function template) [edit]
[edit] Example
Run this code
#include <iomanip> #include <iostream> #include <map> #include <random> #include <string> int main() { std::random_device rd; std::mt19937 gen(rd()); // If an event occurs 4 times a minute on average, how // often is it that it occurs n times in one minute? std::poisson_distribution<> d(4); std::map <int, int> hist; for (int n = 0; n != 10000; ++n) ++hist[d(gen)]; for (auto [x, y] : hist) std::cout << std::hex << x << ' ' << std::string (y / 100, '*') << '\n'; }
Possible output:
0 * 1 ******* 2 ************** 3 ******************* 4 ******************* 5 *************** 6 ********** 7 ***** 8 ** 9 * a b c d
[edit] External links
Weisstein, Eric W. "Poisson Distribution." From MathWorld — A Wolfram Web Resource.