/**
* 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.tools.math.kernels;
import com.rapidminer.tools.Tools;
/**
* Returns the value of the Multiquadric kernel of both examples.
*
* @author Ingo Mierswa
*/
public class MultiquadricKernel extends Kernel {
private static final long serialVersionUID = -7896178642575555770L;
/** The parameter sigma of the Multiquadric kernel. */
private double sigma = 1.0d;
/** The parameter shift of the multiquadric kernel. */
private double shift = 1.0d;
@Override
public int getType() {
return KERNEL_MULTIQUADRIC;
}
public void setSigma(double sigma) {
this.sigma = sigma;
}
public double getSigma() {
return sigma;
}
public void setShift(double shift) {
this.shift = shift;
}
public double getShift() {
return shift;
}
/** Calculates kernel value of vectors x and y. */
@Override
public double calculateDistance(double[] x1, double[] x2) {
return Math.sqrt((norm2(x1, x2) / 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 + "))";
}
@Override
public String toString() {
return "Multiquadric Kernel with" + Tools.getLineSeparator() + " sigma: " + Tools.formatNumber(getSigma())
+ Tools.getLineSeparator() + " shift: " + Tools.formatNumber(getShift());
}
}