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: \(P(i|k, p) = \binom{k + i - 1}{i} \cdot p^k \cdot (1 - p)^i\)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.
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, longlong, unsignedshort, unsignedint, unsignedlong, or unsignedlonglong. |
Member types
| Member type | Definition |
|---|---|
result_type (C++11) | IntType |
param_type (C++11) | the type of the parameter set, see RandomNumberDistribution. |
Member functions
|
(C++11) | constructs new distribution (public member function) |
|
(C++11) | resets the internal state of the distribution (public member function) |
Generation |
|
|
(C++11) | generates the next random number in the distribution (public member function) |
Characteristics |
|
|
(C++11) | returns the distribution parameters (public member function) |
|
(C++11) | gets or sets the distribution parameter object (public member function) |
|
(C++11) | returns the minimum potentially generated value (public member function) |
|
(C++11) | returns the maximum potentially generated value (public member function) |
Non-member functions
|
(C++11)(C++11)(removed in C++20) | compares two distribution objects (function) |
|
(C++11) | performs stream input and output on pseudo-random number distribution (function template) |
Example
#include <iomanip>
#include <iostream>
#include <map>
#include <random>
#include <string>
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 [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 a b
External links
| Weisstein, Eric W. "Negative Binomial Distribution." From MathWorld — A Wolfram Web Resource. |
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