/*
* 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 a Polynomial kernel of both examples.
*
* @author Ingo Mierswa
*/
public class PolynomialKernel extends Kernel {
private static final long serialVersionUID = 1296800822192183260L;
/** The parameter degree of the polynomial kernel. */
private double degree = 3;
/** The parameter shift of the polynomial kernel. */
private double shift = 1.0d;
@Override
public int getType() {
return KERNEL_POLYNOMIAL;
}
public double getDegree() {
return degree;
}
/** Sets the used polynomial parameters. */
public void setPolynomialParameters(double degree, double shift) {
this.degree = degree;
this.shift = shift;
}
/** Subclasses must implement this method. */
@Override
public double calculateDistance(double[] x1, double[] x2) {
double prod = innerProduct(x1, x2) + shift;
double result = prod;
for (int i = 1; i < degree; i++) {
result *= prod;
}
return result;
}
@Override
public String getDistanceFormula(double[] x, String[] attributeConstructions) {
StringBuffer innerProductString = new StringBuffer();
boolean first = true;
for (int i = 0; i < x.length; i++) {
double value = x[i];
if (!Tools.isZero(value)) {
if (value < 0.0d) {
if (first)
innerProductString.append("-" + Math.abs(value) + " * " + attributeConstructions[i]);
else
innerProductString.append(" - " + Math.abs(value) + " * " + attributeConstructions[i]);
} else {
if (first)
innerProductString.append(value + " * " + attributeConstructions[i]);
else
innerProductString.append(" + " + value + " * " + attributeConstructions[i]);
}
first = false;
}
}
StringBuffer result = new StringBuffer("(" + innerProductString.toString() + ")");
for (int i = 1; i < degree; i++) {
result.append(" * (" + innerProductString.toString() + ")");
}
return result.toString();
}
@Override
public String toString() {
return "Polynomial Kernel with" + Tools.getLineSeparator() +
" shift: " + Tools.formatNumber(shift) + Tools.getLineSeparator() +
" degree: " + degree;
}
}