From cppreference.com
template<classRealType=double>classexponential_distribution;(since C++11)Produces random non-negative floating-point values x, distributed according to probability density function:
P(x|λ) = λe-λx
The value obtained is the time/distance until the next random event if random events occur at constant rate λ per unit of time/distance. For example, this distribution describes the time between the clicks of a Geiger counter or the distance between point mutations in a DNA strand.
This is the continuous counterpart of
.
std::exponential_distribution satisfies
.
Template parameters
RealType - The result type generated by the generator. The effect is undefined if this is not one of float, double, or longdouble. Member types
Member type Definition result_type(C++11)RealTypeparam_typethe type of the parameter set, see
. 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
(C++11)
returns the lambda distribution parameter (rate of events)
(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
Notes
Some implementations may occasionally return infinity if RealType is float. This is
.
Example
Run this code
#include<iomanip>#include<iostream>#include<map>#include<random>#include<string>intmain(){std::random_devicerd;std::mt19937gen(rd());// if particles decay once per second on average,// how much time, in seconds, until the next one?std::exponential_distribution<>d(1);std::map<int,int>hist;for(intn=0;n!=10000;++n)++hist[2*d(gen)];for(autoconst&[x,y]:hist)std::cout<<std::fixed<<std::setprecision(1)<<x/2.0<<'-'<<(x+1)/2.0<<' '<<std::string(y/200,'*')<<'\n';}Possible output:
0.0-0.5 ******************* 0.5-1.0 *********** 1.0-1.5 ******* 1.5-2.0 **** 2.0-2.5 ** 2.5-3.0 * 3.0-3.5 3.5-4.0 External links