std::negative_binomial_distribution

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C library
 
std::negative_binomial_distribution
 
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.

Contents

[edit] Member types

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

[edit] Member functions

constructs new distribution
(public member function)
resets the internal state of the distribution
(public member function)
Generation
generates the next random number in the distribution
(public member function)
Characteristics
returns the distribution parameters
(public member function)
gets or sets the distribution parameter object
(public member function)
returns the minimum potentially generated value
(public member function)
returns the maximum potentially generated value
(public member function)

[edit] Non-member functions

compares two distribution objects
(function)
performs stream input and output on pseudo-random number distribution
(function)

[edit] Example

Run this code
#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

[edit] External links

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

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