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(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) | |
Produces random non-negative integer valuesi, distributed according to discrete probability function:
| e-μ ·μi |
| i! |
The value obtained is the probability of exactlyi occurrences of a random event if the expected,mean number of its occurrence under the same conditions (on the same time/space interval) isμ.
std::poisson_distribution satisfiesRandomNumberDistribution.
Contents |
| IntType | - | The result type generated by the generator. The effect is undefined if this is not one ofshort,int,long,longlong,unsignedshort,unsignedint,unsignedlong, orunsignedlonglong. |
| Member type | Definition |
result_type(C++11) | IntType |
param_type(C++11) | the type of the parameter set, seeRandomNumberDistribution. |
(C++11) | constructs new distribution (public member function)[edit] |
(C++11) | resets the internal state of the distribution (public member function)[edit] |
Generation | |
(C++11) | generates the next random number in the distribution (public member function)[edit] |
Characteristics | |
(C++11) | returns themean distribution parameter (mean number of occurrences of the event) (public member function)[edit] |
(C++11) | gets or sets the distribution parameter object (public member function)[edit] |
(C++11) | returns the minimum potentially generated value (public member function)[edit] |
(C++11) | returns the maximum potentially generated value (public member function)[edit] |
(C++11)(C++11)(removed in C++20) | compares two distribution objects (function)[edit] |
(C++11) | performs stream input and output on pseudo-random number distribution (function template)[edit] |
#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 *abcd
| Weisstein, Eric W. "Poisson Distribution." From MathWorld — A Wolfram Web Resource. |
