median_tpl.h

Go to the documentation of this file.

/***************************************************************************
 *   Copyright (C) 2005 by Pierre-Henri WUILLEMIN et Christophe GONZALES   *
 *   {prenom.nom}_at_lip6.fr                                               *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/
#include <sstream>

#include <vector>

// to ease parser in IDEs
#include <agrum/multidim/aggregators/median.h>
#include <agrum/multidim/aggregators/multiDimAggregator.h>

namespace gum {

  namespace aggregator {
    template < typename GUM_SCALAR >
    INLINE Median< GUM_SCALAR >::Median() : MultiDimAggregator< GUM_SCALAR >() {
      GUM_CONSTRUCTOR(Median);
    }

    template < typename GUM_SCALAR >
    INLINE Median< GUM_SCALAR >::Median(const Median< GUM_SCALAR >& from) :
        MultiDimAggregator< GUM_SCALAR >(from) {
      GUM_CONS_CPY(Median);
    }

    template < typename GUM_SCALAR >
    INLINE Median< GUM_SCALAR >::~Median() {
      GUM_DESTRUCTOR(Median);
    }

    template < typename GUM_SCALAR >
    INLINE std::string Median< GUM_SCALAR >::aggregatorName() const {
      std::stringstream ss;
      ss << "median";
      return ss.str();
    }

    template < typename GUM_SCALAR >
    INLINE MultiDimContainer< GUM_SCALAR >*
           Median< GUM_SCALAR >::newFactory() const {
      return new Median< GUM_SCALAR >();
    }

    template < typename GUM_SCALAR >
    Idx Median< GUM_SCALAR >::_buildValue(const gum::Instantiation& i) const {
      if (i.nbrDim() < 2)
        return i.nbrDim() / 2;   // arbitrary. Guess = (max-min)/2 .

      // we assume that every (parent) variable has the same domainSize
      Idx maxVal = i.variable(1).domainSize();

      std::vector< Idx > cum(maxVal, 0);

      for (Idx j = 1; j < this->nbrDim(); j++)
        cum[i.val(j)]++;

      Idx half = (this->nbrDim() + 1) / 2;   // 50% of the population

      Idx max = maxVal;
      for (Idx j = 0, sumcum = 0; j < maxVal; j++)
        if ((sumcum += cum[j]) >= half) {
          max = j;
          break;
        }
      Idx maxR = maxVal;
      for (Idx j = maxVal - 1, jj = 0, sumcum = 0; jj < maxVal; jj++, j--)
        if ((sumcum += cum[j]) >= half) {
          maxR = j;
          break;
        }

      // multiDimAggregator::get will truncate if needed.
      return (maxR + max) / 2;
    }

    template < typename GUM_SCALAR >
    INLINE Idx Median< GUM_SCALAR >::_fold(const DiscreteVariable& v,
                                           Idx                     i1,
                                           Idx                     i2,
                                           bool& stop_iteration) const {
      return 0;
    }

  }   // namespace aggregator
}   // namespace gum