/*
* RapidMiner
*
* Copyright (C) 2001-2011 by Rapid-I and the contributors
*
* Complete list of developers available at our web site:
*
* http://rapid-i.com
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see http://www.gnu.org/licenses/.
*/
package com.rapidminer.operator.learner.functions.kernel.jmysvm.kernel;
import com.rapidminer.tools.Tools;
/**
* Polynomial Kernel
*
* @author Stefan Rueping, Ingo Mierswa
*/
public class KernelPolynomial extends Kernel {
private static final long serialVersionUID = 7385441798122306059L;
private double degree = 2;
/**
* Class constructor
*/
public KernelPolynomial() {};
/**
* Output as String
*/
@Override
public String toString() {
return ("poly(" + degree + ")");
}
public void setDegree(double degree) {
this.degree = degree;
}
/**
* Calculates kernel value of vectors x and y
*/
@Override
public double calculate_K(int[] x_index, double[] x_att, int[] y_index, double[] y_att) {
double prod = innerproduct(x_index, x_att, y_index, y_att);
double result = prod;
for (int i = 1; i < degree; i++) {
result *= prod;
}
return result;
}
@Override
public String getDistanceFormula(double[] x, String[] attributeConstructions) {
StringBuffer innerProductString = new StringBuffer();
boolean first = true;
for (int i = 0; i < x.length; i++) {
double value = x[i];
if (!Tools.isZero(value)) {
if (value < 0.0d) {
if (first)
innerProductString.append("-" + Math.abs(value) + " * " + attributeConstructions[i]);
else
innerProductString.append(" - " + Math.abs(value) + " * " + attributeConstructions[i]);
} else {
if (first)
innerProductString.append(value + " * " + attributeConstructions[i]);
else
innerProductString.append(" + " + value + " * " + attributeConstructions[i]);
}
first = false;
}
}
StringBuffer result = new StringBuffer("(" + innerProductString.toString() + ")");
for (int i = 1; i < degree; i++) {
result.append(" * (" + innerProductString.toString() + ")");
}
return result.toString();
}
public double getDegree() {
return degree;
}
}