NAME¶

std::weibull_distribution - std::weibull_distribution

Synopsis¶

Defined in header <random>
template< class RealType = double > (since C++11)
class weibull_distribution;

The weibull_distribution meets the requirements of a RandomNumberDistribution and
produces random numbers according to the Weibull distribution:

\(\small{f(x;a,b)=\frac{a}{b}{(\frac{x}{b})}^{a-1}\exp{(-{(\frac{x}{b})}^{a})}
}\)f(x;a,b) =

a
b

⎛
⎜
⎝

x
b

⎞
⎟
⎠a-1
exp⎛
⎜
⎝-⎛
⎜
⎝

x
b

⎞
⎟
⎠a
⎞
⎟
⎠

a is the shape parameter and b the scale parameter.

std::weibull_distribution satisfies RandomNumberDistribution.

Template parameters¶

RealType - The result type generated by the generator. The effect is undefined if
this is not one of float, double, or long double.

Member types¶

Member type Definition
result_type (C++11) RealType
param_type (C++11) the type of the parameter set, see RandomNumberDistribution.

Member functions¶

constructor constructs new distribution
(C++11) (public member function)
reset resets the internal state of the distribution
(C++11) (public member function)

Generation¶

operator() generates the next random number in the distribution
(C++11) (public member function)

Characteristics¶

a returns the distribution parameters
b (public member function)
(C++11)
param gets or sets the distribution parameter object
(C++11) (public member function)
min returns the minimum potentially generated value
(C++11) (public member function)
max returns the maximum potentially generated value
(C++11) (public member function)

Non-member functions¶

operator==
operator!= compares two distribution objects
(C++11) (function)
(C++11)(removed in C++20)
operator<< performs stream input and output on pseudo-random number
operator>> distribution
(C++11) (function template)

Example¶

// Run this code

#include <cmath>
#include <iomanip>
#include <iostream>
#include <map>
#include <random>
#include <string>

int main()
{
std::random_device rd;
std::mt19937 gen(rd());

std::weibull_distribution<> d;

std::map<int, int> hist;
for (int n = 0; n != 10000; ++n)
++hist[std::round(d(gen))];

std::cout << std::fixed << std::setprecision(1) << std::hex;
for (auto [x, y] : hist)
std::cout << x << ' ' << std::string(y / 200, '*') << '\n';
}

Possible output:¶

0 *******************
1 *******************
2 ******
3 **
4
5
6
7
8

External links¶

1. Weisstein, Eric W. "Weibull Distribution." From MathWorld — A Wolfram Web
Resource.
2. Weibull distribution — From Wikipedia.