Chi2TestPolicy_tpl.h

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/***************************************************************************
 *   Copyright (C) 2005 by Christophe GONZALES and Pierre-Henri WUILLEMIN  *
 *   {prenom.nom}_at_lip6.fr                                               *
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 *   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     *
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 ***************************************************************************/
// =========================================================================
#include <agrum/FMDP/learning/core/testPolicy/Chi2TestPolicy.h>
// =========================================================================


namespace gum {


  // ##########################################################################
  //
  // ##########################################################################

  // ==========================================================================
  //
  // ==========================================================================
  template < typename GUM_SCALAR >
  void Chi2TestPolicy< GUM_SCALAR >::addObservation(Idx iattr, GUM_SCALAR ivalue) {
    ITestPolicy< GUM_SCALAR >::addObservation(iattr, ivalue);
    __conTab.add(iattr, ivalue);
  }


  // ############################################################################
  // @name Test result
  // ############################################################################

  // ============================================================================
  // Computes the GStat of current variable according to the test
  // ============================================================================
  template < typename GUM_SCALAR >
  void Chi2TestPolicy< GUM_SCALAR >::computeScore() const {
    ITestPolicy< GUM_SCALAR >::computeScore();
    __chi2Score = 0;
    for (auto attrIter = __conTab.attrABeginSafe();
         attrIter != __conTab.attrAEndSafe();
         ++attrIter) {
      double semiExpected =
         (double)(attrIter.val()) / (double)this->nbObservation();
      for (auto valIter = __conTab.attrBBeginSafe();
           valIter != __conTab.attrBEndSafe();
           ++valIter) {
        double cell = (double)__conTab.joint(attrIter.key(), valIter.key());
        if (cell < 5) continue;
        double expected = semiExpected * (double)(valIter.val());

        __chi2Score += std::pow(cell - expected, 2.0) / expected;
      }
    }
  }

  // ============================================================================
  // Returns the performance of current variable according to the test
  // ============================================================================
  template < typename GUM_SCALAR >
  double Chi2TestPolicy< GUM_SCALAR >::score() const {
    if (this->_isModified()) computeScore();
    double score =
       1
       - ChiSquare::probaChi2(
            __chi2Score, (__conTab.attrASize() - 1) * (__conTab.attrBSize() - 1));
    return score;
  }

  // ============================================================================
  // Returns a second criterion to severe ties
  // ============================================================================
  template < typename GUM_SCALAR >
  double Chi2TestPolicy< GUM_SCALAR >::secondaryscore() const {
    if (this->_isModified()) computeScore();
    return __chi2Score;
  }

  template < typename GUM_SCALAR >
  void Chi2TestPolicy< GUM_SCALAR >::add(const Chi2TestPolicy< GUM_SCALAR >& src) {
    ITestPolicy< GUM_SCALAR >::add(src);
    __conTab += src.ct();
  }

}   // End of namespace gum