/*
* 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;
/**
* Gaussian Combination Kernel
*
* @author Ingo Mierswa
*/
public class KernelMultiquadric extends Kernel {
private static final long serialVersionUID = -9152135200919885773L;
private double sigma = 1;
private double shift = 1;
/** Output as String */
@Override
public String toString() {
return ("multiquadric(sigma=" + sigma + ",shift=" + shift + ")");
};
/** Class constructor. */
public KernelMultiquadric() {}
public void setParameters(double sigma, double shift) {
this.sigma = sigma;
this.shift = shift;
}
/** 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) {
return Math.sqrt((norm2(x_index, x_att, y_index, y_att) / sigma) + (shift * shift));
}
@Override
public String getDistanceFormula(double[] x, String[] attributeConstructions) {
StringBuffer norm2Expression = new StringBuffer();
boolean first = true;
for (int i = 0; i < x.length; i++) {
double value = x[i];
String valueString = "(" + value + " - " + attributeConstructions[i] + ")";
if (first) {
norm2Expression.append(valueString + " * " + valueString);
} else {
norm2Expression.append(" + " + valueString + " * " + valueString);
}
first = false;
}
return "sqrt((" + norm2Expression + " / " + sigma + ") + (" + shift + " * " + shift + "))";
}
}