I confess that I am no expert in C++.

I am looking for a fast way to compute weighted median, which Boost seemed to have. But it seems I am not able to make it work.

#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;
}

produces the following output, which is clearly wrong.

         Median: 0.3
Weighted Median: 0.3

Am I doing something wrong? Any help will be greatly appreciated.

* however, the weighted sum works correctly *

@glowcoder: The weighted sum works perfectly fine like this.

#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;
}

and the result is

         Sum: 2.1
Weighted Sum: 1.5