is Boost Library's weighted median broken?
- by user624188
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
