std::poisson_distribution

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编译时合理的算法 （C++11）
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std::poisson_distribution
成员函数
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Member functions
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poisson_distribution::poisson_distribution
poisson_distribution::reset
代
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Generation
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poisson_distribution::operator()
特性
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Characteristics
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poisson_distribution::mean
poisson_distribution::param
poisson_distribution::min
poisson_distribution::max
非成员函数
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Non-member functions
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operator==
operator!=
operator<<
operator>>
 
Defined in header <random>
template< class IntType = int >
class poisson_distribution;
 （C++11 起）
产生随机的非负整数值i根据离散概率函数，分布：
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Produces random non-negative integer values i, distributed according to discrete probability function:
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P(i|μ) =
e-μ
·μi
i!

The value obtained is the probability of exactly i occurrences of a random event if the expected, mean number of its occurrence under the same conditions (on the same time/space interval) is μ.

目录

[编辑] 会员类型

会员类型
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Member type
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 Definition
result_type IntType
param_type
的类型的参数集，未指定
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the type of the parameter set, unspecified
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[编辑] 成员函数
构建新的分配
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constructs new distribution
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（公共成员函数） [edit]
复位内部状态的分布
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resets the internal state of the distribution
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（公共成员函数） [edit]
代
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Generation
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生成下一个随机数的分布
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generates the next random number in the distribution
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（公共成员函数） [edit]
特性
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Characteristics
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 returns the mean distribution parameter (mean number of occurrences of the event)
（公共成员函数） [edit]
获取或设置的分布参数对象
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gets or sets the distribution parameter object
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（公共成员函数） [edit]
返回的最低可能产生的价值
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returns the minimum potentially generated value
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（公共成员函数） [edit]
返回的最大潜在价值
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returns the maximum potentially generated value
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（公共成员函数） [edit]

[编辑] 非成员函数
比较两个分布对象
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compares two distribution objects
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（函数） [edit]
执行流输入和输出的伪随机数分布
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performs stream input and output on pseudo-random number distribution
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（函数） [edit]

[编辑] 为例

#include <iostream>
#include <iomanip>
#include <string>
#include <map>
#include <random>
int main()
{
    std::random_device rd;
    std::mt19937 gen(rd());
 
    // if an event occurs 4 times a minute on average
    // how often is it that it occurs n times in one minute?
    std::poisson_distribution<> d(4);
 
    std::map<int, int> hist;
    for(int n=0; n<10000; ++n) {
        ++hist[d(gen)];
    }
    for(auto p : hist) {
        std::cout << p.first <<
                ' ' << std::string(p.second/100, '*') << '\n';
    }
}

Output: 

0 *
1 *******
2 **************
3 *******************
4 *******************
5 ***************
6 **********
7 *****
8 **
9 *
10 
11 
12 
13

[编辑] 外部链接

Weisstein, Eric W. "Poisson Distribution."，从MathWorld - Wolfram网络资源.
Original:
Weisstein, Eric W. "Poisson Distribution." From MathWorld--A Wolfram Web Resource.
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来自“http://zh.cppreference.com/mwiki/index.php?title=cpp/numeric/random/poisson_distribution&oldid=27652”