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ChiSquareDistance.h
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ChiSquareDistance.h
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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 3 of the License, or
* (at your option) any later version.
*
* Written (W) 2008-2009 Christian Gehl
* Copyright (C) 2008-2009 Fraunhofer Institute FIRST
*/
#ifndef __CHISQUAREDISTANCE_H__
#define __CHISQUAREDISTANCE_H__
#include <shogun/lib/config.h>
#include <shogun/lib/common.h>
#include <shogun/distance/DenseDistance.h>
namespace shogun
{
/** @brief class ChiSquareDistance
*
* This implementation of \f$\chi^{2}\f$ distance extends the
* concept of \f$\chi^{2}\f$ metric to negative values.
*
* \f[\displaystyle
* d(\bf{x},\bf{x'}) = \sum_{i=1}^{n}\frac{(x_{i}-x'_{i})^2}
* {|x_{i}|+|x'_{i}|} \quad \bf{x},\bf{x'} \in R^{n}
* \f]
*
* @see K. Rieck, P. Laskov. Linear-Time Computation of Similarity Measures
* for Sequential Data. Journal of Machine Learning Research, 9:23--48,2008.
*/
class CChiSquareDistance: public CDenseDistance<float64_t>
{
public:
/** default constructor */
CChiSquareDistance();
/** constructor
*
* @param l features of left-hand side
* @param r features of right-hand side
*/
CChiSquareDistance(CDenseFeatures<float64_t>* l, CDenseFeatures<float64_t>* r);
virtual ~CChiSquareDistance();
/** init distance
*
* @param l features of left-hand side
* @param r features of right-hand side
* @return if init was successful
*/
virtual bool init(CFeatures* l, CFeatures* r);
/** cleanup distance */
virtual void cleanup();
/** get distance type we are
*
* @return distance type CHISQUARE
*/
virtual EDistanceType get_distance_type() { return D_CHISQUARE; }
/** get name of the distance
*
* @return name Chi-square distance
*/
virtual const char* get_name() const { return "ChiSquareDistance"; }
protected:
/// compute distance for features a and b
/// idx_{a,b} denote the index of the feature vectors
/// in the corresponding feature object
virtual float64_t compute(int32_t idx_a, int32_t idx_b);
};
} // namespace shogun
#endif /* _CHISQUAREDISTANCE_H___ */