c++ - Boost Library的加权中位数被打破了吗？

我承认我不是C++专家。

我正在寻找一种计算Boost中位数的加权中位数的快速方法。
但似乎我无法使其工作。

#include <iostream>
#include <boost/accumulators/accumulators.hpp>
#include <boost/accumulators/statistics/stats.hpp>
#include <boost/accumulators/statistics/median.hpp>
#include <boost/accumulators/statistics/weighted_median.hpp>
using namespace boost::accumulators;

int main()
{
  // Define an accumulator set
  accumulator_set<double, stats<tag::median > > acc1;
  accumulator_set<double, stats<tag::median >, float> acc2;

  // push in some data ...
  acc1(0.1);
  acc1(0.2);
  acc1(0.3);
  acc1(0.4);
  acc1(0.5);
  acc1(0.6);

  acc2(0.1, weight=0.);
  acc2(0.2, weight=0.);
  acc2(0.3, weight=0.);
  acc2(0.4, weight=1.);
  acc2(0.5, weight=1.);
  acc2(0.6, weight=1.);

  // Display the results ...
  std::cout << "         Median: " << median(acc1) << std::endl;
  std::cout << "Weighted Median: " << median(acc2) << std::endl;

  return 0;
}

产生以下输出，这显然是错误的。

         Median: 0.3
Weighted Median: 0.3

难道我做错了什么？
任何帮助将不胜感激。

*但是，加权总和可以正常工作*

@glowcoder:加权总和可以像这样完美地工作。

#include <iostream>
#include <boost/accumulators/accumulators.hpp>
#include <boost/accumulators/statistics/stats.hpp>
#include <boost/accumulators/statistics/sum.hpp>
#include <boost/accumulators/statistics/weighted_sum.hpp>
using namespace boost::accumulators;

int main()
{
  // Define an accumulator set
  accumulator_set<double, stats<tag::sum > > acc1;
  accumulator_set<double, stats<tag::sum >, float> acc2;
  // accumulator_set<double, stats<tag::median >, float> acc2;

  // push in some data ...
  acc1(0.1);
  acc1(0.2);
  acc1(0.3);
  acc1(0.4);
  acc1(0.5);
  acc1(0.6);

  acc2(0.1, weight=0.);
  acc2(0.2, weight=0.);
  acc2(0.3, weight=0.);
  acc2(0.4, weight=1.);
  acc2(0.5, weight=1.);
  acc2(0.6, weight=1.);

  // Display the results ...
  std::cout << "         Median: " << sum(acc1) << std::endl;
  std::cout << "Weighted Median: " << sum(acc2) << std::endl;

  return 0;
}

结果是

         Sum: 2.1
Weighted Sum: 1.5

最佳答案

boost 功能未损坏。

问题在于您没有提供足够的数据来使P ^ 2估计器起作用。如果围绕数据输入(例如)

for(int i=0;i<100000;i++){
  acc2(0.1, weight=0.);
  acc2(0.2, weight=0.);
  acc2(0.3, weight=0.);
  acc2(0.4, weight=1.);
  acc2(0.5, weight=1.);
  acc2(0.6, weight=1.);
}

您得到正确的结果

Median: 0.3
Weighted Median: 0.5

或者，您可以指定

 accumulator_set<double,
    stats<tag::weighted_median(with_p_square_cumulative_distribution) >,
    double> acc2 ( p_square_cumulative_distribution_num_cells = 5 );

即使您的问题中仅添加了6点，它也给出了Weighted Median: 0.55作为答案。

关于c++ - Boost Library的加权中位数被打破了吗？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/5111304/