Defined in header <random> | ||
|---|---|---|
template<
class RealType = double
>
class normal_distribution;
| (since C++11) |
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⎛Here \(\small\mu\)μ is the Mean and \(\small\sigma\)σ is the Standard deviation (stddev).
std::normal_distribution satisfies all requirements of RandomNumberDistribution.
| RealType | - | The result type generated by the generator. The effect is undefined if this is not one of float, double, or long double. |
| Member type | Definition |
|---|---|
result_type (C++11) | RealType |
param_type (C++11) | the type of the parameter set, see RandomNumberDistribution. |
|
(C++11) | constructs new distribution (public member function) |
|
(C++11) | resets the internal state of the distribution (public member function) |
Generation |
|
|
(C++11) | generates the next random number in the distribution (public member function) |
Characteristics |
|
|
(C++11) | returns the distribution parameters (public member function) |
|
(C++11) | gets or sets the distribution parameter object (public member function) |
|
(C++11) | returns the minimum potentially generated value (public member function) |
|
(C++11) | returns the maximum potentially generated value (public member function) |
|
(C++11)(C++11)(removed in C++20) | compares two distribution objects (function) |
|
(C++11) | performs stream input and output on pseudo-random number distribution (function template) |
#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';
}Possible output:
-2 -1 0 1 * 2 *** 3 ****** 4 ******** 5 ********** 6 ******** 7 ***** 8 *** 9 * 10 11 12
| 1. | Weisstein, Eric W. "Normal Distribution." From MathWorld — A Wolfram Web Resource. |
| 2. | Normal distribution — From Wikipedia. |
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