NICE_VisLearning/classifier/fpclassifier/randomforest/SCGiniIndex.h

/**
 * @file SCGiniIndex.h
 * @brief the Gini index splitting criterion
 * @author Sven Sickert
 * @date 01/16/2017

*/
#ifndef SCGiniIndexINCLUDE
#define SCGiniIndexINCLUDE

#include "SplittingCriterion.h"

namespace OBJREC {

class SCGiniIndex : public SplittingCriterion
{
  protected:

    double gini_left,
           gini_right,
           count_left,
           count_right;

    /**
     * @brief computation of Gini index
     * @param distribution given distribution
     * @param count amount of samples
     * @param maxClassNo maximum class number
     * @return computed Gini index
     */
    double computeGiniIndex(
        const double* distribution,
        const double count ,
        const int maxClassNo );

  public:

    /* default constructor */
    SCGiniIndex();

    /* simple constructor */
    SCGiniIndex( int _min_examples );

    /** config constructor */
    SCGiniIndex( const NICE::Config *conf );

    /** copy constructor */
    SCGiniIndex( const SCGiniIndex &obj );

    /* simple destructor */
    virtual ~SCGiniIndex();

    /* cloning function */
    virtual SplittingCriterion* clone();

    /**
     * @brief evaluate the split and return if split is possible
     * @param values unsorted list of feature values of a certain dimension
     * @param threshold threshold for current feature dimension
     * @param distribution_left class distribution for left child node after splitting
     * @param distribution_right class distribution for right child node after splitting
     * @param maxClassNo maximum class number
     * @return possible split or not
     */
    virtual bool evaluateSplit(
        const FeatureValuesUnsorted & values,
        double threshold,
        double* distribution_left,
        double* distribution_right,
        int maxClassNo );

    /**
     * @brief compute purity based on given split
     * @return purity value
     */
    double computePurity() const;

};

} // namespace


#endif