source: trunk/lib/svm/PolynomialKernelFunction.h @ 353

// $Id: PolynomialKernelFunction.h 353 2005-06-08 23:28:35Z peter $

#ifndef _theplu_svm_polynomial_kernel_function_
#define _theplu_svm_polynomial_kernel_function_

#include <c++_tools/svm/KernelFunction.h>
#include <c++_tools/gslapi/vector.h>

#include <cmath>


namespace theplu {

namespace gslapi {
  class vector;
}

namespace svm {

  ///
  /// 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$
    ///   
    inline double operator()(const gslapi::vector& a1,
                             const gslapi::vector& a2) const
      { return ((order_>1) ? pow(1+a1*a2,order_) : a1*a2); }


    ///
    ///returning the scalar product of two vectors in feature space using the
    ///polynomial kernel with weights.
    ///   
    double operator()(const gslapi::vector&, const gslapi::vector&, 
                      const gslapi::vector&, const gslapi::vector&) const;
    
  private:
    int order_;

  }; // class PolynomialKernelFunction

}} // of namespace svm and namespace theplu

#endif