Difference between revisions of "cpp/numeric/random/poisson distribution"
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Revision as of 17:10, 19 April 2012
Template:cpp/numeric/random/poisson distribution/sidebar
| Defined in header <random>
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| template< class IntType = int > class poisson_distribution; |
(since C++11) | |
Produces random non-negative integer values i, distributed according to discrete probability function:
- P(i|μ) =
e-μ·μi i!
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.
Contents |
Member types
Template:tdcl list begin Template:tdcl list hitem Template:tdcl list item Template:tdcl list item Template:tdcl list end
Member functions
Non-member functions
Example
Run this code
#include <iostream> #include <iomanip> #include <string> #include <map> #include <random> 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 p : hist) { std::cout << p.first << ' ' << std::string(p.second/100, '*') << '\n'; } }
Output:
0 * 1 ******* 2 ************** 3 ******************* 4 ******************* 5 *************** 6 ********** 7 ***** 8 ** 9 * 10 11 12 13
External links
Weisstein, Eric W. "Poisson Distribution." From MathWorld--A Wolfram Web Resource.
