/**
* 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 simple inner product of both examples.
*
* @author Ingo Mierswa
*/
public class DotKernel extends Kernel {
private static final long serialVersionUID = -7737835520088841652L;
@Override
public int getType() {
return KERNEL_DOT;
}
/** Subclasses must implement this method. */
@Override
public double calculateDistance(double[] x1, double[] x2) {
return innerProduct(x1, x2);
}
@Override
public String getDistanceFormula(double[] x, String[] attributeConstructions) {
StringBuffer result = 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) {
result.append("-" + Math.abs(value) + " * " + attributeConstructions[i]);
} else {
result.append(" - " + Math.abs(value) + " * " + attributeConstructions[i]);
}
} else {
if (first) {
result.append(value + " * " + attributeConstructions[i]);
} else {
result.append(" + " + value + " * " + attributeConstructions[i]);
}
}
first = false;
}
}
return result.toString();
}
@Override
public String toString() {
return "Dot Kernel";
}
}