std::lognormal_distribution
From cppreference.com
| Defined in header <random>
|
||
template< class RealType = double >
class lognormal_distribution;
|
(since C++11) | |
The lognormal_distribution random number distribution produces random numbers x > 0 according to a Log-normal distribution:
- f(x; m,s) =
exp⎛1 sx√2 π
⎜
⎝-
⎞(ln x - m)2 2s2
⎟
⎠
The parameters m and s are, respectively, the mean and standard deviation of the natural logarithm of x.
std::lognormal_distribution satisfies all requirements of RandomNumberDistribution.
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 (C++11)
|
RealType
|
param_type (C++11)
|
the type of the parameter set, see RandomNumberDistribution. |
Member functions
(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) |
Non-member functions
(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) |
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());
std::lognormal_distribution<> d(1.6, 0.25);
std::map<int, int> hist;
for (int n = 0; n < 1e4; ++n)
++hist[std::round(d(gen))];
for (std::cout << std::fixed << std::setprecision(1); auto [x, y] : hist)
std::cout << std::hex << x << ' ' << std::string(y / 200, '*') << '\n';
}
Possible output:
2
3 ***
4 *************
5 ***************
6 *********
7 ****
8 *
9
a
b
c
External links
| Weisstein, Eric W. "Log Normal Distribution." From MathWorld — A Wolfram Web Resource. |