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(C++11)(C++11)(until C++20) | ||||
(C++11)(C++11) |
Defined in header <random> | ||
template<class RealType=double> class lognormal_distribution; | (since C++11) | |
The lognormal_distribution random number distribution produces random numbersx > 0 according to aLog-normal distribution:
| 1 |
| sx√2 π |
| (ln x - m)2 |
| 2s2 |
The parametersm ands are, respectively, the mean and standard deviation of the natural logarithm ofx.
std::lognormal_distribution satisfies all requirements ofRandomNumberDistribution.
Contents |
| RealType | - | The result type generated by the generator. The effect is undefined if this is not one offloat,double, orlongdouble. |
| Member type | Definition |
result_type(C++11) | RealType |
param_type(C++11) | the type of the parameter set, seeRandomNumberDistribution. |
(C++11) | constructs new distribution (public member function)[edit] |
(C++11) | resets the internal state of the distribution (public member function)[edit] |
Generation | |
(C++11) | generates the next random number in the distribution (public member function)[edit] |
Characteristics | |
(C++11) | returns the distribution parameters (public member function)[edit] |
(C++11) | gets or sets the distribution parameter object (public member function)[edit] |
(C++11) | returns the minimum potentially generated value (public member function)[edit] |
(C++11) | returns the maximum potentially generated value (public member function)[edit] |
(C++11)(C++11)(removed in C++20) | compares two distribution objects (function)[edit] |
(C++11) | performs stream input and output on pseudo-random number distribution (function template)[edit] |
#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:
23 ***4 *************5 ***************6 *********7 ****8 *9abc
| Weisstein, Eric W. "Log Normal Distribution." From MathWorld — A Wolfram Web Resource. |
