chi2_inl.h

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 *       - Pierre-Henri WUILLEMIN(_at_LIP6)                                 *
 *       - Christophe GONZALES(_at_AMU)                                     *
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 *       - Pierre-Henri WUILLEMIN(_at_LIP6)                                 *
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#pragma once

 
 
namespace gum {
 
  // sets the conditioning nodes (useful for computing degrees of freedom)
  INLINE void Chi2::setConditioningNodes(const std::vector< Idx >& db_conditioning_ids) {
    _conditioning_size_ = 1;
    for (Idx i = 0; i < db_conditioning_ids.size(); ++i) {
      _conditioning_size_ *= _modalities_[db_conditioning_ids[i]];
    }
  }
 
  // returns the number of degrees of freedom
  INLINE Size Chi2::degreesOfFreedom(const std::pair< Idx, Idx >& pair) {
    return degreesOfFreedom(pair.first, pair.second);
  }
 
  // returns the number of degrees of freedom
  INLINE Size Chi2::degreesOfFreedom(Idx var1, Idx var2) {
    return (_conditioning_size_ * (_modalities_[var1] - 1) * (_modalities_[var2] - 1));
  }
 
  // computes the critical value according to the number of degrees of freedom
  ALWAYS_INLINE double Chi2::criticalValue(const std::pair< Idx, Idx >& pair) {
    return criticalValue(pair.first, pair.second);
  }
 
  // computes the critical value according to the number of degrees of freedom
  ALWAYS_INLINE double Chi2::criticalValue(Idx var1, Idx var2) {
    Size DF = degreesOfFreedom(var1, var2);
 
    // try to see if the threshold is not already in cache
    try {
      return _critical_values_[DF];
    } catch (const Exception&) {
      // here we have to compute the threshold of the chi2
      // we use Gary Perlman's algorithm
      double value = _criticalValue_(_confidence_proba_, DF);
      _critical_values_.insert(DF, value);
      return value;
    }
  }
 
  // modifies the confidence proba
  INLINE void Chi2::setConfidenceProba(double new_proba) {
    // if we did not change the confidence proba, do nothing
    if (_confidence_proba_ == new_proba) return;
 
    _confidence_proba_ = new_proba;
 
    // remove the currently stored critical values
    _critical_values_.clear();
  }
 
} /* namespace gum */