Namespace
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std::exponential_distribution

Da cppreference.com.
< cpp‎ | numeric‎ | random

 
 
Numeri libreria
Comuni funzioni matematiche
Virgola mobile ambiente
I numeri complessi
Array numerici
Pseudo-casuale generazione
In fase di compilazione aritmetica razionale (C++11)
Generici operazioni numeriche
Original:
Generic numeric operations
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iota(C++11)
accumulate
inner_product
adjacent_difference
partial_sum
 
Pseudo-casuale generazione
Motori e adattatori del motore
Original:
Engines and engine adaptors
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linear_congruential_engine(C++11)
mersenne_twister_engine(C++11)
subtract_with_carry_engine(C++11)
discard_block_engine(C++11)
independent_bits_engine(C++11)
shuffle_order_engine(C++11)
Generatori
Original:
Generators
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random_device(C++11)
Distribuzioni
Original:
Distributions
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Distribuzioni uniformi
Original:
Uniform distributions
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uniform_int_distribution(C++11)
uniform_real_distribution(C++11)
generate_canonical(C++11)
Bernoulli distribuzioni
Original:
Bernoulli distributions
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bernoulli_distribution(C++11)
binomial_distribution(C++11)
negative_binomial_distribution(C++11)
geometric_distribution(C++11)
Poisson distribuzioni
Original:
Poisson distributions
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poisson_distribution(C++11)
exponential_distribution(C++11)
gamma_distribution(C++11)
weibull_distribution(C++11)
extreme_value_distribution(C++11)
Distribuzioni normali
Original:
Normal distributions
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normal_distribution(C++11)
lognormal_distribution(C++11)
chi_squared_distribution(C++11)
cauchy_distribution(C++11)
fisher_f_distribution(C++11)
student_t_distribution(C++11)
Distribuzioni di campionamento
Original:
Sampling distributions
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discrete_distribution(C++11)
piecewise_constant_distribution(C++11)
piecewise_linear_distribution(C++11)
Seed Sequenze
Original:
Seed Sequences
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seed_seq(C++11)
Libreria C
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C library
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rand
srand
RAND_MAX
 
std::exponential_distribution
Membri funzioni
Original:
Member functions
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exponential_distribution::exponential_distribution
exponential_distribution::reset
Generazione
Original:
Generation
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exponential_distribution::operator()
Caratteristiche
Original:
Characteristics
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exponential_distribution::lambda
exponential_distribution::param
exponential_distribution::min
exponential_distribution::max
Non membri funzioni
Original:
Non-member functions
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operator==
operator!=
operator<<
operator>>
 
Defined in header <random>
template< class RealType = double >
class exponential_distribution;
(dal C++11)
Produce casuali non negativi valori a virgola mobile x, distribuiti in base alla funzione di densità di probabilità:
Original:
Produces random non-negative floating-point values x, distributed according to probability density function:
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P(x|λ) = λe-λx
Il valore ottenuto è il tempo / distanza fino al prossimo evento casuale se si verificano eventi casuali a velocità costante λ per unità di tempo / distanza. Ad esempio, questa distribuzione descrive il tempo tra gli scatti di un contatore Geiger o la distanza tra mutazioni puntiformi in un filamento di DNA.
Original:
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.
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Questa è la controparte continua di std::geometric_distribution
Original:
This is the continuous counterpart of std::geometric_distribution
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Indice

[modifica] Membri tipi

Membro tipo
Original:
Member type
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Definition
result_type RealType
param_type
il tipo di set di parametri, non specificato
Original:
the type of the parameter set, unspecified
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[modifica] Membri funzioni

costruisce nuova distribuzione
Original:
constructs new distribution
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(membro pubblico funzione) [edit]
ripristina lo stato interno della distribuzione
Original:
resets the internal state of the distribution
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(membro pubblico funzione) [edit]
Generazione
Original:
Generation
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genera il successivo numero casuale nella distribuzione
Original:
generates the next random number in the distribution
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(membro pubblico funzione) [edit]
Caratteristiche
Original:
Characteristics
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restituisce la distribuzione' lambda parametro (tasso di eventi)
Original:
returns the lambda distribution parameter (rate of events)
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(membro pubblico funzione) [edit]
ottiene o imposta l'oggetto parametro di distribuzione
Original:
gets or sets the distribution parameter object
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(membro pubblico funzione) [edit]
restituisce il valore minimo potenzialmente generato
Original:
returns the minimum potentially generated value
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(membro pubblico funzione) [edit]
restituisce il valore massimo potenzialmente generato
Original:
returns the maximum potentially generated value
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(membro pubblico funzione) [edit]

[modifica] Non membri funzioni

confronta due oggetti di distribuzione
Original:
compares two distribution objects
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(funzione) [edit]
esegue flusso di ingresso e di uscita sul pseudo-casuale distribuzione numerica
Original:
performs stream input and output on pseudo-random number distribution
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(funzione) [edit]

[modifica] Esempio

#include <iostream>
#include <iomanip>
#include <string>
#include <map>
#include <random>
int main()
{
    std::random_device rd;
    std::mt19937 gen(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(int n=0; n<10000; ++n) {
        ++hist[2*d(gen)];
    }
    for(auto p : hist) {
        std::cout << std::fixed << std::setprecision(1) 
                  << p.first/2.0 << '-' << (p.first+1)/2.0 <<
                ' ' << std::string(p.second/200, '*') << '\n';
    }

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

[modifica] Collegamenti esterni

Weisstein, Eric W. "Exponential Distribution." Da MathWorld - Una risorsa Web Wolfram.
Original:
Weisstein, Eric W. "Exponential Distribution." From MathWorld--A Wolfram Web Resource.
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