001    /*
002     * JNI_SVM-light - A Java Native Interface for SVM-light
003     * 
004     * Copyright (C) 2005 
005     * Tom Crecelius & Martin Theobald 
006     * Max-Planck Institute for Computer Science
007     * 
008     * This program is free software; you can redistribute it and/or modify it under
009     * the terms of the GNU General Public License as published by the Free Software
010     * Foundation.
011     * 
012     * This program is distributed in the hope that it will be useful, but WITHOUT
013     * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
014     * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
015     * details.
016     * 
017     * You should have received a copy of the GNU General Public License along with
018     * this program; if not, write to the Free Software Foundation, Inc., 51
019     * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
020     */
021    
022    package jnisvmlight;
023    
024    /**
025     * A polynomial kernel.
026     * 
027     * @author Tom Crecelius & Martin Theobald
028     */
029    public class PolynomialKernel extends ExtendedKernel {
030    
031      private double m_order;
032    
033      protected PolynomialKernel() {
034        this(new LinearKernel(), 3.0, 1.0, 1.0);
035      }
036    
037      public PolynomialKernel(Kernel nestedKernel, double order, double a, double c) {
038        super(nestedKernel, a, c);
039        this.m_order = order;
040      }
041    
042      public double evaluate(FeatureVector v1, FeatureVector v2) {
043        return Math.pow(m_a * m_kernel.evaluate(v1, v2) + m_c, m_order);
044      }
045    
046      public double getOrder() {
047        return m_order;
048      }
049    
050      public void setOrder(double order) {
051        this.m_order = order;
052      }
053    
054      public String toString() {
055        return "Polynomial kernel K(x, y | k) = (" + m_a + " * k(x, y) + " + m_c
056            + ")^" + m_order + ". k = " + m_kernel.toString();
057      }
058    }