SAMScore.h

#ifndef _theplu_yat_statistics_sam_score_
#define _theplu_yat_statistics_sam_score_

// $Id: SAMScore.h 2119 2009-12-12 23:11:43Z peter $

/*
  Copyright (C) 2006, 2007, 2008 Jari Häkkinen, Peter Johansson

  This file is part of the yat library, http://dev.thep.lu.se/yat

  The yat library 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 3 of the
  License, or (at your option) any later version.

  The yat library 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 yat. If not, see <http://www.gnu.org/licenses/>.
*/

#include "Score.h"

#include <cmath>

namespace theplu {
namespace yat {
  namespace utility {
    class VectorBase;
  }
  namespace classifier {
    class DataLookWeighted1D;
  }
namespace statistics {  

  class SAMScore : public Score
  {

  public:
    SAMScore(const double s0, bool absolute=true);

    double score(const classifier::Target& target, 
                 const utility::VectorBase& value) const; 

    double score(const classifier::Target& target, 
                 const classifier::DataLookupWeighted1D& value) const;          

    double score(const classifier::Target& target, 
                 const utility::VectorBase& value, 
                 const utility::VectorBase& weight) const;          
  private:
    double s0_;

    template<class T> 
    double score(const T& positive, const T& negative) const
    {
      if(positive.n()+negative.n()<=2) 
        return 0;
      double diff = positive.mean() - negative.mean();
      double s2 = ( (1.0/positive.n()+1.0/negative.n()) * 
                    (positive.sum_xx_centered()+negative.sum_xx_centered()) /
                    (positive.n()+negative.n()-2) );
      if (diff<0 && absolute_)
        return -diff/(sqrt(s2)+s0_);
      return diff/(sqrt(s2)+s0_);
    }
  };

}}} // of namespace statistics, yat, and theplu

#endif