std:: normal_distribution

Generates random numbers according to the Normal (or Gaussian) random number distribution . It is defined as:

\(\small{f(x;\mu,\sigma)}=\frac{1}{\sigma\sqrt{2\pi} }\exp{(-\frac{1}{2}{(\frac{x-\mu}{\sigma})}^2)}\) f(x; μ,σ) =

1

σ √ 2π

exp ⎛
⎜
⎝

-1

2

⎛
⎜
⎝

x-μ

σ

⎞
⎟
⎠ 2 ⎞
⎟
⎠

Here \(\small\mu\) μ is the Mean and \(\small\sigma\) σ is the Standard deviation ( stddev ).

std::normal_distribution satisfies all requirements of RandomNumberDistribution .

Template parameters

Member types

Member functions

Non-member functions

Example

#include <cmath>
#include <iomanip>
#include <iostream>
#include <map>
#include <random>
#include <string>
 
int main()
{
    std::random_device rd{};
    std::mt19937 gen{rd()};
 
    // values near the mean are the most likely
    // standard deviation affects the dispersion of generated values from the mean
    std::normal_distribution d{5.0, 2.0};
 
    // draw a sample from the normal distribution and round it to an integer
    auto random_int = [&d, &gen]{ return std::round(d(gen)); };
 
    std::map<int, int> hist{};
    for (int n = 0; n != 10000; ++n)
        ++hist[random_int()];
 
    for (auto [x, y] : hist)
        std::cout << std::setw(2) << x << ' ' << std::string(y / 200, '*') << '\n';
}

-2
-1
 0
 1 *
 2 ***
 3 ******
 4 ********
 5 **********
 6 ********
 7 *****
 8 ***
 9 *
10
11
12

External links