std::lognormal_distribution

template <class RealType = double> class lognormal_distribution;

Lognormal distribution

Random number distribution that produces floating-point values according to a lognormal distribution, which is described by the following probability density function:

This distribution produces random numbers whose logarithms are normally distributed (see normal_distribution).

The distribution parameters (m and s) relate to the characteristics of that underlying normal distribution.

To produce a random value following this distribution, call its member function operator().

Template parameters

RealType: A floating-point type. Aliased as member type result_type.
By default, this is double.

Member types

The following aliases are member types of lognormal_distribution:

member type	definition	notes
`result_type`	The first template parameter (`RealType`)	The type of the numbers generated (defaults to `double`)
`param_type`	not specified	The type returned by member param.

Member functions

(constructor): Construct lognormal distribution (public member function)

operator(): Generate random number (public member function)

reset: Reset distribution (public member function)

param: Distribution parameters (public member function)

min: Minimum value (public member function)

max: Maximum value (public member function)

Distribution parameters:

lognormal_distribution::m: Parameter m (public member function)

lognormal_distribution::s: Parameter s (public member function)

Non-member functions

operator<<: Insert into output stream (function template)

operator>>: Extract from input stream (function template)

relational operators: Relational operators (function template)

Example

// lognormal_distribution #include <iostream> #include <random> int main() { const int nrolls=10000; // number of experiments const int nstars=100; // maximum number of stars to distribute std::default_random_engine generator; std::lognormal_distribution<double> distribution(0.0,1.0); int p[10]={}; for (int i=0; i<nrolls; ++i) { double number = distribution(generator); if ((number>=0.0)&&(number<10.0)) ++p[int(number)]; } std::cout << "lognormal_distribution (0.0,1.0):" << std::endl; for (int i=0; i<10; ++i) { std::cout << i << "-" << (i+1) << ": "; std::cout << std::string(p[i]*nstars/nrolls,'*') << std::endl; } return 0; }

Possible output:

lognormal_distribution (0.0,1.0): 0-1: ************************************************** 1-2: ************************** 2-3: ********** 3-4: ***** 4-5: ** 5-6: * 6-7: 7-8: 8-9: 9-10:

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non-member functions