/**
* 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;
/**
* Returns the value of the Epanechnikov kernel of both examples.
*
* @author Ingo Mierswa
*/
public class KernelEpanechnikov extends Kernel {
private static final long serialVersionUID = -1706678102534775619L;
/** The parameter sigma of the Epanechnikov kernel. */
private double sigma = 1.0d;
/** The parameter degree of the Epanechnikov kernel. */
private double degree = 1;
/** Constructor(s) */
public KernelEpanechnikov(double sigma, double degree) {
super();
this.sigma = sigma;
this.degree = degree;
}
public KernelEpanechnikov() {
super();
}
@Override
public double eval(double[] x, double[] y) {
double expression = norm2(x, y) / sigma;
if (expression > 1) {
return 0.0d;
} else {
double minus = 1.0d - expression;
return Math.pow(minus, degree);
}
}
@Override
public String toString() {
return "epanechnikov kernel [sigma = " + sigma + ", degree = " + degree + "]";
}
}