std::weibull_distribution

 

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std::weibull_distribution

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>>

 

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.

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, unspecified

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.