std::weibull_distribution

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

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

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`	RealType
`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
ab	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>
#include <cmath>
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))];
    }
    for(auto p : hist) {
        std::cout << std::fixed << std::setprecision(1) << std::setw(2)
                  << p.first << ' ' << std::string(p.second/200, '*') << '\n';
    }
}

Output:

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

External links

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

Language
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Language support library
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Common mathematical functions
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iota (C++11)
accumulate
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random_device (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)
gamma_distribution (C++11)
weibull_distribution (C++11)
extreme_value_distribution (C++11)
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normal_distribution (C++11)
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student_t_distribution (C++11)
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discrete_distribution (C++11)
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piecewise_linear_distribution (C++11)
Seed Sequences
seed_seq (C++11)
C library
rand
srand
RAND_MAX

Member functions
weibull_distribution::weibull_distribution
weibull_distribution::reset
Generation
weibull_distribution::operator()
Characteristics
weibull_distribution::aweibull_distribution::b
weibull_distribution::param
weibull_distribution::min
weibull_distribution::max
Non-member functions
operator==operator!=
operator<<operator>>