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: \({\small f(x;m,s) = \frac{1}{sx\sqrt{2\pi} } \exp{(-\frac{ {(\ln{x} - m)}^{2} }{2{s}^{2} })} }\)f(x; m,s) =

1/sx√2 π exp

⎝- (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 RealType
param_type(C++11) the type of the parameter set, see RandomNumberDistribution.

Member functions

constructs new distribution
(public member function)
resets the internal state of the distribution
(public member function)
generates the next random number in the distribution
(public member function)
returns the distribution parameters
(public member function)
gets or sets the distribution parameter object
(public member function)
returns the minimum potentially generated value
(public member function)
returns the maximum potentially generated value
(public member function)

Non-member functions

(C++11)(C++11)(removed in C++20)
compares two distribution objects
performs stream input and output on pseudo-random number distribution
(function template)


#include <iostream>
#include <iomanip>
#include <string>
#include <map>
#include <random>
#include <cmath>
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<10000; ++n) {
    for(auto p : hist) {
        std::cout << std::fixed << std::setprecision(1) << std::setw(2)
                  << p.first << ' ' << std::string(p.second/200, '*') << '\n';

Possible output:

 3 ***
 4 *************
 5 ***************
 6 *********
 7 ****
 8 *

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