[rand.dist.norm.lognormal]

# 29 Numerics library [[numerics]](./#numerics)

## 29.5 Random number generation [[rand]](rand#dist.norm.lognormal)

### 29.5.9 Random number distribution class templates [[rand.dist]](rand.dist#norm.lognormal)

#### 29.5.9.5 Normal distributions [[rand.dist.norm]](rand.dist.norm#lognormal)

#### 29.5.9.5.2 Class template lognormal_distribution [rand.dist.norm.lognormal]

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L5774)

A lognormal_distribution random number distribution
produces random numbers x>0 distributed according to
the probability density function in Formula [29.14](#eq:rand.dist.norm.lognormal)[.](#1.sentence-1)

p(x|m,s)=1sxâ2Ïâexp(â(lnxâm)22s2)(29.14)

[ð](#lib:lognormal_distribution_)

namespace std {template<class RealType = double>class lognormal_distribution {public:// typesusing result_type = RealType; using param_type = *unspecified*; // constructor and reset functions lognormal_distribution() : lognormal_distribution(0.0) {}explicit lognormal_distribution(RealType m, RealType s = 1.0); explicit lognormal_distribution(const param_type& parm); void reset(); // equality operatorsfriend bool operator==(const lognormal_distribution& x, const lognormal_distribution& y); // generating functionstemplate<class URBG> result_type operator()(URBG& g); template<class URBG> result_type operator()(URBG& g, const param_type& parm); // property functions RealType m() const;
 RealType s() const;
 param_type param() const; void param(const param_type& parm);
 result_type min() const;
 result_type max() const; // inserters and extractorstemplate<class charT, class traits>friend basic_ostream<charT, traits>&operator<<(basic_ostream<charT, traits>& os, const lognormal_distribution& x); template<class charT, class traits>friend basic_istream<charT, traits>&operator>>(basic_istream<charT, traits>& is, lognormal_distribution& x); };}

[ð](#lib:lognormal_distribution,constructor)

`explicit lognormal_distribution(RealType m, RealType s = 1.0);
`

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L5836)

*Preconditions*: 0<s[.](#2.sentence-1)

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L5840)

*Remarks*: m and s correspond to the respective parameters of the distribution[.](#3.sentence-1)

[ð](#lib:m,lognormal_distribution)

`RealType m() const;
`

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L5852)

*Returns*: The value of the m parameter
 with which the object was constructed[.](#4.sentence-1)

[ð](#lib:s,lognormal_distribution)

`RealType s() const;
`

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L5864)

*Returns*: The value of the s parameter
 with which the object was constructed[.](#5.sentence-1)
