source: trunk/c++_tools/classifier/PolynomialKernelFunction.h @ 675

#ifndef _theplu_classifier_polynomial_kernel_function_
#define _theplu_classifier_polynomial_kernel_function_

// $Id$

/*
  Copyright (C) The authors contributing to this file.

  This file is part of the yat library, http://lev.thep.lu.se/trac/yat

  The yat library 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 (at your option) any later version.

  The yat library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  02111-1307, USA.
*/

#include "yat/classifier/KernelFunction.h"
#include "yat/classifier/DataLookup1D.h"


#include <cmath>


namespace theplu {
namespace classifier {

  ///
  /// Class for polynomial kernel calculations
  ///

 
  class PolynomialKernelFunction : public KernelFunction 
  {
    
  public:
    ///
    ///Constructor taking the order of the polynomial as input. Default is
    ///order=1 yielding the linear kernel function.
    ///
    PolynomialKernelFunction(int = 1);
    
    ///
    ///Destructor
    ///
    virtual ~PolynomialKernelFunction(void) {};
    
    ///
    /// returning the scalar product of two vectors in feature space using the
    /// polynomial kernel. @return If order is larger than one: \f$ (1+x \cdot
    /// y)^{order} \f$ \n If order is one (linear): \f$ x \cdot y \f$
    ///   
    double operator()(const DataLookup1D& a1, const DataLookup1D& a2) const;

    ///
    /// @return If order is larger than one: \f$ (1+x \cdot y)^{order}
    /// \f$ \n If order is one (linear): \f$ \sum w_yxy \f$
    ///
    ///
    double operator()(const DataLookup1D& x, 
                      const DataLookupWeighted1D& y) const;
    ///
    /// returning the scalar product of two vectors in feature space
    /// using the polynomial kernel with weights. Having all weights
    /// equal to unity yields the same as non-weighted version.
    ///
    /// @return If order is larger than one: \f$ (1+x \cdot y)^{order}
    /// \f$ \n If order is one (linear): \f$ \sum w_xw_yxy \f$
    ///
    double operator()(const DataLookupWeighted1D& x, 
                      const DataLookupWeighted1D& y) const;


  private:
    int order_;

  }; // class PolynomialKernelFunction

}} // of namespace classifier and namespace theplu

#endif