/**
* Copyright (C) 2001-2017 by RapidMiner and the contributors
*
* Complete list of developers available at our web site:
*
* http://rapidminer.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;
/**
* Radial basis function (rbf) kernel: K(x, y) = exp(-lengthScale^{-2} * ||x - y||^2)
*
* @author Piotr Kasprzak, Ingo Mierswa
*/
public class KernelRadial extends Kernel {
private static final long serialVersionUID = 2728320273018583212L;
/** LengthScale parameter */
protected double lengthScale = 0;
/** Constructor(s) */
public KernelRadial(double lengthScale) {
super();
this.lengthScale = lengthScale;
}
public KernelRadial() {
super();
}
/** evaluate kernel */
@Override
public double eval(double[] x, double[] y) {
double result = Math.exp(-1.0d / (lengthScale * lengthScale) * norm2(x, y));
return result;
}
@Override
public String toString() {
return "rbf kernel [lengthScale = " + lengthScale + "]";
}
}