source: trunk/yat/statistics/SNR.cc @ 781

// $Id: SNR.cc 781 2007-03-05 19:44:03Z peter $

/*
  Copyright (C) The authors contributing to this file.

  This file is part of the yat library, http://lev.thep.lu.se/trac/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 2 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 this program; if not, write to the Free Software
  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  02111-1307, USA.
*/

#include "SNR.h"
#include "Averager.h"
#include "AveragerWeighted.h"
#include "yat/classifier/DataLookupWeighted1D.h"
#include "yat/classifier/Target.h"
#include "yat/utility/vector.h"

#include <cassert>

namespace theplu {
namespace yat {
namespace statistics {  

  SNR::SNR(bool b) 
    : Score(b), score_(0)
  {
  }

  double SNR::score(const classifier::Target& target, 
                    const utility::vector& value)
  {
    statistics::Averager positive;
    statistics::Averager negative;
    for(size_t i=0; i<target.size(); i++){
      if (target.binary(i))
        positive.add(value(i));
      else
        negative.add(value(i));
    }
    double diff = positive.mean() - negative.mean();
    double denom=positive.std()+negative.std();
    score_=diff/denom;
    if(positive.n()==0 || negative.n()==0) 
      score_=0;
    if (score_<0 && absolute_)
      score_=-score_;    
    return score_;
  }

  double SNR::score(const classifier::Target& target, 
                    const classifier::DataLookupWeighted1D& value)
  {
    statistics::AveragerWeighted positive;
    statistics::AveragerWeighted negative;
    for(size_t i=0; i<target.size(); i++){
      if (target.binary(i))
        positive.add(value.data(i),value.weight(i));
      else
        negative.add(value.data(i),value.weight(i));
    }
    double diff = positive.mean() - negative.mean();
    double denom=positive.std()+negative.std();
    assert(denom);
    score_=diff/denom;
    if(positive.sum_w()==0 || negative.sum_w()==0) 
      score_=0;
    if (score_<0 && absolute_)
      score_=-score_;    
    return score_;
  }



  double SNR::score(const classifier::Target& target, 
                    const utility::vector& value,
                    const utility::vector& weight)
  {
    statistics::AveragerWeighted positive;
    statistics::AveragerWeighted negative;
    for(size_t i=0; i<target.size(); i++){
      if (target.binary(i))
        positive.add(value(i),weight(i));
      else
        negative.add(value(i),weight(i));
    }
    double diff = positive.mean() - negative.mean();
    double denom=positive.std()+negative.std();
    assert(denom);
    score_=diff/denom;
    if(positive.sum_w()==0 || negative.sum_w()==0) 
      score_=0;
    if (score_<0 && absolute_)
      score_=-score_;    
    return score_;
  }

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