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std::normal_distribution

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< cpp‎ | numeric‎ | random
Revision as of 17:52, 2 November 2012 by P12bot (Talk | contribs)

 
 
 
 
 
Defined in header <random>
template< class RealType = double >
class normal_distribution;
(since C++11)

Normal (or Guassian) random number distribution:

f(x; μ,σ) =
1
σ
exp

-
1
2


x-μ
σ


2


With the mean μ and the standard deviation (stddev) σ.

Contents

Member types

Member type Definition
result_type RealType
param_type the type of the parameter set, unspecified

Member functions

Template:cpp/numeric/random/distribution/dcl list constructorTemplate:cpp/numeric/random/distribution/dcl list resetTemplate:cpp/numeric/random/distribution/dcl list operator()Template:cpp/numeric/random/normal distribution/dcl list meanTemplate:cpp/numeric/random/normal distribution/dcl list stddevTemplate:cpp/numeric/random/distribution/dcl list paramTemplate:cpp/numeric/random/distribution/dcl list minTemplate:cpp/numeric/random/distribution/dcl list max
Generation
Characteristics

Non-member functions

Template:cpp/numeric/random/distribution/dcl list operator cmpTemplate:cpp/numeric/random/distribution/dcl list operator ltltgtgt

Example

#include <iostream>
#include <iomanip>
#include <string>
#include <map>
#include <random>
#include <cmath>
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(5,2);
 
    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:

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

External links