Chi2TestPolicy_tpl.h

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 *       - Pierre-Henri WUILLEMIN(_at_LIP6)                                 *
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#pragma once
 

// =========================================================================
#include <agrum/FMDP/learning/core/testPolicy/Chi2TestPolicy.h>
 
// =========================================================================
 
 
namespace gum {
 
 
  // ##########################################################################
  //
  // ##########################################################################
 
  // ==========================================================================
  //
  // ==========================================================================
  template < typename GUM_ELEMENT >
  void Chi2TestPolicy< GUM_ELEMENT >::addObservation(Idx iattr, GUM_ELEMENT ivalue) {
    ITestPolicy< GUM_ELEMENT >::addObservation(iattr, ivalue);
    _conTab_.add(iattr, ivalue);
  }
 
  // ############################################################################
  // @name Test result
  // ############################################################################
 
  // ============================================================================
  // Computes the GStat of current variable according to the test
  // ============================================================================
  template < typename GUM_ELEMENT >
  void Chi2TestPolicy< GUM_ELEMENT >::computeScore() const {
    ITestPolicy< GUM_ELEMENT >::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_ELEMENT >
  double Chi2TestPolicy< GUM_ELEMENT >::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_ELEMENT >
  double Chi2TestPolicy< GUM_ELEMENT >::secondaryscore() const {
    if (this->isModified_()) computeScore();
    return _chi2Score_;
  }
 
  template < typename GUM_ELEMENT >
  void Chi2TestPolicy< GUM_ELEMENT >::add(const Chi2TestPolicy< GUM_ELEMENT >& src) {
    ITestPolicy< GUM_ELEMENT >::add(src);
    _conTab_ += src.ct();
  }
 
  template < typename GUM_ELEMENT >
  Chi2TestPolicy< GUM_ELEMENT >::Chi2TestPolicy() :
      ITestPolicy< GUM_ELEMENT >(), _conTab_(), _chi2Score_(0) {
    GUM_CONSTRUCTOR(Chi2TestPolicy);
  }
 
  template < typename GUM_ELEMENT >
  Chi2TestPolicy< GUM_ELEMENT >::~Chi2TestPolicy() {
    GUM_DESTRUCTOR(Chi2TestPolicy);
    ;
  }
 
  template < typename GUM_ELEMENT >
  void* Chi2TestPolicy< GUM_ELEMENT >::operator new(size_t s) {
    return SmallObjectAllocator::instance().allocate(s);
  }
 
  template < typename GUM_ELEMENT >
  void Chi2TestPolicy< GUM_ELEMENT >::operator delete(void* p) {
    SmallObjectAllocator::instance().deallocate(p, sizeof(Chi2TestPolicy));
  }
 
  template < typename GUM_ELEMENT >
  bool Chi2TestPolicy< GUM_ELEMENT >::isTestRelevant() const {
    return (this->nbObservation() > 20 && this->nbObservation() > _conTab_.attrASize() * 5);
  }
 
  template < typename GUM_ELEMENT >
  const ContingencyTable< Idx, GUM_ELEMENT >& Chi2TestPolicy< GUM_ELEMENT >::ct() const {
    return _conTab_;
  }
 
  template < typename GUM_ELEMENT >
  std::string Chi2TestPolicy< GUM_ELEMENT >::toString() const {
    return std::format("{}\t\t\tContingency Table : \n{}\n\t\t\tGStat : {}\n\t\t\tGStat : {}\n",
                       ITestPolicy< GUM_ELEMENT >::toString(),
                       _conTab_.toString(),
                       this->score(),
                       this->secondaryscore());
  }
 
}   // End of namespace gum