std::normal_distribution
From cppreference.com
C++
Feature test macros (C++20)
Concepts library (C++20)
Metaprogramming library (C++11)
Ranges library (C++20)
Filesystem library (C++17)
Concurrency support library (C++11)
Execution control library (C++26)
Numerics library
Mathematical special functions (C++17)
Mathematical constants (C++20)
Basic linear algebra algorithms (C++26)
Data-parallel types (SIMD) (C++26)
Floating-point environment (C++11)
Bit manipulation (C++20)
Saturation arithmetic (C++26)
(C++17)
(C++17)
(C++17)
(C++17)
(C++17)
(C++17)
Pseudo-random number generation
(C++20)
(C++11)
(C++11)
(C++11)
(C++26)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++26)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
normal_distribution
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
std::normal_distribution
Member functions
(C++11)
Generation
(C++11)
Characteristics
(C++11)(C++11)
(C++11)
(C++11)
(C++11)
Non-member functions
(C++11)(C++11)(until C++20)
(C++11)(C++11)
Defined in header
<random>
template< class RealType = double >
class normal_distribution;
(since C++11)
class 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) = 1σ√2πexp⎛
⎜
⎝-12⎛
⎜
⎝x-μσ⎞
⎟
⎠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.
Contents
[edit] 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.
[edit] Member types
Member type
Definition
result_type (C++11)
RealType
[edit] Member functions
Generation
Characteristics
[edit] Non-member functions
(C++11)
(function template) [edit]
[edit] 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()}; // 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::lround (d(gen)); }; std::map <long, unsigned> histogram{}; for (auto n{10000}; n; --n) ++histogram[random_int()]; for (const auto [k, v] : histogram) std::cout << std::setw (2) << k << ' ' << std::string (v / 200, '*') << '\n'; }
Possible output:
-1 0 1 * 2 *** 3 ***** 4 ******** 5 ********* 6 ********* 7 ****** 8 *** 9 * 10 11
[edit] External links
1.
Weisstein, Eric W. "Normal Distribution." From MathWorld — A Wolfram Web Resource.
2.
Normal distribution — From Wikipedia.