C++产生正态分布

1.求均值

 double sum = std::accumulate(std::begin(resultSet), std::end(resultSet), 0.0);
 double mean =  sum / resultSet.size(); //均值

 2.求方差

 double accum  = 0.0;
 std::for_each (std::begin(resultSet), std::end(resultSet), [&](const double d) {
     accum  += (d-mean)*(d-mean);
 });

 double stdev = sqrt(accum/(resultSet.size()-1)); //方差

3.求正太分布值密度函数

double  LogNormal( double  x, double  miu, double  sigma)  //对数正态分布概率密度函数
{
        return  1.0/(x* sqrt (2*PI)*sigma) *  exp (-1*( log (x)-miu)*( log (x)-miu)/(2*sigma*sigma));
}

4.求正态分布随机数

     std::default_random_engine e; //引擎
     std::normal_distribution<double> n(mean, stdev); //均值, 方差
     std::vector vals(9);
     for(std::size_t i=0; i != 200; ++i) {
         unsigned v = std::lround(n(e)); //取整-最近的整数
         if (v < vals.size())
             ++vals[v];
     }
     for (std::size_t j=0; j != vals.size(); ++j)
         std::cout << j << " : " << vals[j] << std::string(vals[j], '*') << std::endl;