source: trunk/src/NNI.cc @ 173

// $Id: NNI.cc 173 2004-09-28 22:50:09Z jari $

#include <algorithm>
#include <cmath>
#include <fstream>

#include "stl_utility.h"
#include "NNI.h"

namespace theplu {
namespace cpptools {

  using namespace std;

  NNI::NNI(gslapi::matrix& matrix,const gslapi::matrix& weight,
           const u_int neighbours)
    : data_(matrix), imputed_data_(matrix), neighbours_(neighbours),
      weight_(weight)
  {
  }



// d_{ij}^2=\frac {\sum_{1,N} w_{il} w_{jl} (x_{il}-x_{jl})^2 }
//                {\sum_{l,N} w_{il} w_{jl} }
  vector<pair<u_int,double> > NNI::calculate_distances(const u_int row) const
  {
    vector<pair<u_int,double> > distance;
    for (size_t i=0; i<data_.rows(); i++)
      if (i!=row) {
        double contribs=0;
        pair<u_int,double> this_distance(i,0.0);
        for (size_t j=0; j<data_.columns(); j++)
          // 0 contribution for missing values
          if (weight_(i,j) && weight_(row,j)) {
            double weight_factor=weight_(i,j)*weight_(row,j);
            this_distance.second+=( weight_factor *
                                    (data_(i,j)-data_(row,j)) *
                                    (data_(i,j)-data_(row,j)) );
            contribs+=weight_factor;
          }
        if (contribs) { // ignore lines without any contributions
          this_distance.second=sqrt(this_distance.second/contribs);
          distance.push_back(this_distance);
        }
      }
    return distance;
  }



  vector<u_int> NNI::nearest_neighbours(const u_int column,
                                        const vector<pair<u_int,double> >& d) const
  {
    vector<u_int> index;
    double contribs=0;
    for (u_int i=0; ((i<d.size()) &&
                     (contribs+=weight_(d[i].first,column))<=neighbours_); i++)
      if (weight_(d[i].first,column))
        index.push_back(i);
    return index;
  }


}} // of namespace cpptools and namespace theplu