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#ifndef MEDIAN_H
#define MEDIAN_H
// This file is part of libigl, a simple c++ geometry processing library.
//
// Copyright (C) 2013 Alec Jacobson <alecjacobson@gmail.com>
//
// This Source Code Form is subject to the terms of the Mozilla Public License
// v. 2.0. If a copy of the MPL was not distributed with this file, You can
// obtain one at http://mozilla.org/MPL/2.0/.
#include <Eigen/Dense>
#include <vector>
namespace igl
{
template <typename DerivedM>
void matrix_to_list(const Eigen::DenseBase<DerivedM>& M,
std::vector<typename DerivedM::Scalar> &V)
{
using namespace std;
V.resize(M.size());
// loop over cols then rows
for(int j =0; j<M.cols();j++)
{
for(int i = 0; i < M.rows();i++)
{
V[i+j*M.rows()] = M(i,j);
}
}
}
// Compute the median of an eigen vector
//
// Inputs:
// V #V list of unsorted values
// Outputs:
// m median of those values
// Returns true on success, false on failure
template <typename DerivedV, typename mType>
bool median(
const Eigen::MatrixBase<DerivedV> & V, mType & m)
{
using namespace std;
if(V.size() == 0)
{
return false;
}
vector<typename DerivedV::Scalar> vV;
matrix_to_list(V,vV);
// http://stackoverflow.com/a/1719155/148668
size_t n = vV.size()/2;
nth_element(vV.begin(),vV.begin()+n,vV.end());
if(vV.size()%2==0)
{
nth_element(vV.begin(),vV.begin()+n-1,vV.end());
m = 0.5*(vV[n]+vV[n-1]);
}else
{
m = vV[n];
}
return true;
}
}
#endif
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