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 parameter m is the mean and the parameter s the standard deviation.
| Contents | 
[edit] Member types
| Member type | Definition | 
| result_type | RealType | 
| param_type | the type of the parameter set, unspecified | 
[edit] Member functions
| constructs new distribution (public member function) | |
| resets the internal state of the distribution (public member function) | |
| Generation | |
| generates the next random number in the distribution (public member function) | |
| Characteristics | |
| 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) | |
[edit] Non-member functions
| compares two distribution objects (function) | |
| performs stream input and output on pseudo-random number distribution (function) | 
[edit] Example
Run this code
#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) { ++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 3 *** 4 ************* 5 *************** 6 ********* 7 **** 8 * 9 10 11 12
[edit] External links
- Weisstein, Eric W. "Log Normal Distribution." From MathWorld--A Wolfram Web Resource.
- Log-normal distribution. From Wikipedia.


