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 ⎞ ⎟ ⎠ \cdot p k \cdot (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.

std::negative_binomial_distribution satisfies RandomNumberDistribution

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.

Member types

Member type	Definition
`result_type`	IntType
`param_type`	the type of the parameter set, see RandomNumberDistribution.

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
pk	returns the distribution parameters (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 template)

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

External links

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

Language
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Common mathematical functions
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Compile-time rational arithmetic (C++11)
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gcd (C++17)
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iota (C++11)
accumulate
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Uniform random bit generators
UniformRandomBitGenerator (C++20)
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linear_congruential_engine (C++11)
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Non-deterministic generator
random_device (C++11)
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uniform_int_distribution (C++11)
uniform_real_distribution (C++11)
generate_canonical (C++11)
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bernoulli_distribution (C++11)
binomial_distribution (C++11)
negative_binomial_distribution (C++11)
geometric_distribution (C++11)
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poisson_distribution (C++11)
exponential_distribution (C++11)
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normal_distribution (C++11)
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discrete_distribution (C++11)
piecewise_constant_distribution (C++11)
piecewise_linear_distribution (C++11)
Seed Sequences
seed_seq (C++11)
C library
rand
srand
RAND_MAX

Member functions
negative_binomial_distribution::negative_binomial_distribution
negative_binomial_distribution::reset
Generation
negative_binomial_distribution::operator()
Characteristics
negative_binomial_distribution::pnegative_binomial_distribution::k
negative_binomial_distribution::param
negative_binomial_distribution::min
negative_binomial_distribution::max
Non-member functions
operator==operator!=
operator<<operator>>