std::negative_binomial_distribution

 

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std::negative_binomial_distribution

Member functions

negative_binomial_distribution::negative_binomial_distribution

negative_binomial_distribution::reset

Generation

negative_binomial_distribution::operator()

Characteristics

negative_binomial_distribution::p

negative_binomial_distribution::k

negative_binomial_distribution::param

negative_binomial_distribution::min

negative_binomial_distribution::max

Non-member functions

operator== operator!=

operator<< operator>>

 

Defined in header <random>
template< class IntType = int > class negative_binomial_distribution;		(since C++11)

Produces random non-negative integer values i, distributed according to discrete probability function:

P(i|k,p) =⎛
⎜
⎝k + i − 1
i⎞
⎟
⎠ · pk
· (1 − p)i

The value represents the number of failures in a series of independent yes/no trials (each succeeds with probability p), before exactly k successes occur.

Member types

Member type	Definition
result_type	IntType
param_type	the type of the parameter set, unspecified

Member functions

(constructor)	constructs new distribution (public member function)
reset	resets the internal state of the distribution (public member function)
Generation
operator()	generates the next random number in the distribution (public member function)
Characteristics
k	returns the k distribution parameter (number of trial failures) (public member function)
p	returns the p distribution parameter (probability of a trial generating true) (public member function)
param	gets or sets the distribution parameter object (public member function)
min	returns the minimum potentially generated value (public member function)
max	returns the maximum potentially generated value (public member function)

Non-member functions

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

Example

#include <iostream>
#include <iomanip>
#include <string>
#include <map>
#include <random>
 
int main()
{
    std::random_device rd;
    std::mt19937 gen(rd());
    // Pat goes door-to-door selling cookies
    // At each house, there's a 75% chance that she sells one box
    // how many times will she be turned away before selling 5 boxes?
    std::negative_binomial_distribution<> d(5, 0.75);
 
    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

External links

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