/*
* RapidMiner
*
* Copyright (C) 2001-2008 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.rvm.kernel;
/**
* Laplace kernel:
* K(x, y) = exp(-sqrt(lengthScale^{-2} * ||x - y||^2))
*
* @author Piotr Kasprzak, Ingo Mierswa
* @version $Id: KernelLaplace.java,v 1.3 2008/05/09 19:23:26 ingomierswa Exp $
*/
public class KernelLaplace extends KernelRadial {
private static final long serialVersionUID = -6119888769441823765L;
/** Constructor(s) */
public KernelLaplace() {}
public KernelLaplace(double lengthScale) {
super(lengthScale);
}
/** evaluate kernel */
public double eval(double[] x, double[] y) {
double result = Math.exp(-Math.sqrt(Math.pow(lengthScale, -2) * norm2(x, y)));
return result;
}
public String toString() {
return "laplace kernel [lengthScale = " + lengthScale + "]";
}
}