/*
* 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.tools.math.kernels;
import com.rapidminer.tools.Tools;
/**
* Returns the value of the RBF kernel of both examples.
*
* @author Ingo Mierswa
*/
public class RBFKernel extends Kernel {
private static final long serialVersionUID = 2928962529445448574L;
/** The parameter gamma of the RBF kernel. */
private double gamma = -1.0d;
@Override
public int getType() {
return KERNEL_RADIAL;
}
public void setGamma(double gamma) {
this.gamma = -gamma;
}
public double getGamma() {
return -gamma;
}
/** Calculates kernel value of vectors x and y. */
@Override
public double calculateDistance(double[] x1, double[] x2) {
return (Math.exp(this.gamma * norm2(x1, x2))); // gamma = -params.gamma
}
@Override
public String getDistanceFormula(double[] x, String[] attributeConstructions) {
StringBuffer result = new StringBuffer("exp(");
result.append(gamma + " * (");
boolean first = true;
for (int i = 0; i < x.length; i++) {
double value = x[i];
String valueString = "(" + value + " - " + attributeConstructions[i] + ")";
if (first) {
result.append(valueString + " * " + valueString);
} else {
result.append(" + " + valueString + " * " + valueString);
}
first = false;
}
result.append("))");
return result.toString();
}
@Override
public String toString() {
return "RBF Kernel with" + Tools.getLineSeparator() + " gamma: " + Tools.formatNumber(getGamma());
}
}