std::extreme_value_distribution
From cppreference.com
Defined in header <random> | ||
template<class RealType =double> class extreme_value_distribution; | (since C++11) | |
Produces random numbers according to the Generalized extreme value distribution (it is also known as Gumbel Type I, log-Weibull, Fisher-Tippett Type I):
- p(x;a,b) =
exp⎛1 b
⎜
⎝
- exp⎛a-x b
⎜
⎝
⎞a-x b
⎟
⎠⎞
⎟
⎠
std::extreme_value_distribution satisfies all requirements of RandomNumberDistribution.
Contents |
[edit]Template parameters
| RealType | - | The result type generated by the generator. The effect is undefined if this is not one of float, double, or longdouble. |
[edit]Member types
| Member type | Definition |
result_type(C++11) | RealType |
param_type(C++11) | the type of the parameter set, see RandomNumberDistribution. |
[edit]Member functions
(C++11) | constructs new distribution (public member function) |
(C++11) | resets the internal state of the distribution (public member function) |
Generation | |
(C++11) | generates the next random number in the distribution (public member function) |
Characteristics | |
(C++11) | returns the distribution parameters (public member function) |
(C++11) | gets or sets the distribution parameter object (public member function) |
(C++11) | returns the minimum potentially generated value (public member function) |
(C++11) | returns the maximum potentially generated value (public member function) |
[edit]Non-member functions
(C++11)(C++11)(removed in C++20) | compares two distribution objects (function) |
(C++11) | performs stream input and output on pseudo-random number distribution (function template) |
[edit]Example
Run this code
#include <algorithm>#include <cmath>#include <iomanip>#include <iostream>#include <map>#include <random>#include <vector> template<int Height =5, int BarWidth =1, int Padding =1, int Offset =0, class Seq>void draw_vbars(Seq&& s, constbool DrawMinMax =true){ static_assert(0< Height and 0< BarWidth and 0<= Padding and 0<= Offset); auto cout_n =[](auto&& v, int n =1){while(n-->0)std::cout<< v;}; constauto[min, max]=std::minmax_element(std::cbegin(s), std::cend(s)); std::vector<std::div_t> qr;for(typedef decltype(*std::cbegin(s)) V; V e : s) qr.push_back(std::div(std::lerp(V(0), 8* Height, (e -*min)/(*max -*min)), 8)); for(auto h{Height}; h-->0; cout_n('\n')){ cout_n(' ', Offset); for(auto dv : qr){constauto q{dv.quot}, r{dv.rem};unsignedchar d[]{0xe2, 0x96, 0x88, 0};// Full Block: '█' q < h ? d[0]=' ', d[1]=0: q == h ? d[2]-=(7- r):0; cout_n(d, BarWidth), cout_n(' ', Padding);} if(DrawMinMax && Height >1) Height -1== h ?std::cout<<"┬ "<<*max: h ?std::cout<<"│ ":std::cout<<"┴ "<<*min;}} int main(){std::random_device rd{};std::mt19937 gen{rd()}; std::extreme_value_distribution<> d{-1.618f, 1.618f}; constint norm =10'000; const float cutoff = 0.000'3f; std::map<int, int> hist{};for(int n =0; n != norm;++n)++hist[std::round(d(gen))]; std::vector<float> bars;std::vector<int> indices;for(constauto&[n, p]: hist)if(constfloat x = p *(1.0f/ norm); x > cutoff){ bars.push_back(x); indices.push_back(n);} draw_vbars<8,4>(bars); for(int n : indices)std::cout<<' '<<std::setw(2)<< n <<" ";std::cout<<'\n';}
Possible output:
████ ▅▅▅▅ ┬ 0.2186 ████ ████ │ ▁▁▁▁ ████ ████ ▇▇▇▇ │ ████ ████ ████ ████ │ ████ ████ ████ ████ ▆▆▆▆ │ ████ ████ ████ ████ ████ ▁▁▁▁ │ ▄▄▄▄ ████ ████ ████ ████ ████ ████ ▃▃▃▃ │ ▁▁▁▁ ████ ████ ████ ████ ████ ████ ████ ████ ▆▆▆▆ ▃▃▃▃ ▂▂▂▂ ▁▁▁▁ ▁▁▁▁ ▁▁▁▁ ▁▁▁▁ ┴ 0.0005 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10
[edit]External links
| Weisstein, Eric W. "Extreme Value Distribution." From MathWorld — A Wolfram Web Resource. |
