std::weibull_distribution(3)

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.