/*
 *  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 Anova (RBF) kernel of both examples.
 * 
 * @author Ingo Mierswa
 */
public class AnovaKernel extends Kernel {

	private static final long serialVersionUID = -2955083072613762504L;

	/** The parameter gamma of the Anova kernel. */
	private double gamma = -1.0d;
	
	/** The parameter degree of the Anova kernel. */
	private double degree;
	
	@Override
	public int getType() {
		return KERNEL_ANOVA;
	}

	public void setGamma(double gamma) {
		this.gamma = -gamma;
	}
	
	public void setDegree(double degree) {
		this.degree = degree;
	}

	public double getGamma() {
		return -gamma;
	}

	/** Calculates kernel value of vectors x and y. */
	@Override
	public double calculateDistance(double[] x1, double[] x2) {		
		double result = 0;
		int zeros = x1.length;
		for (int i = 0; i < x1.length; i++) {
			double factor = x1[i] - x2[i];
			result += Math.exp(gamma * factor * factor);
			if (Tools.isNotEqual(x1[i], 0.0d) || Tools.isNotEqual(x2[i], 0.0d)) {
				zeros--;
			}
		}
		result += zeros;
		return Math.pow(result, degree);
	}
	
	@Override
	public String getDistanceFormula(double[] x, String[] attributeConstructions) {
		StringBuffer result = new StringBuffer();
		result.append("pow((");
		
		boolean first = true;
		for (int i = 0; i < x.length; i++) {
			double value = x[i];
			String valueString = "(" + value + " - " + attributeConstructions[i] + ")"; 
			if (first) {
				result.append("exp(-" + Math.abs(gamma) + " * " + valueString + " * " + valueString + ")");
			} else {
				result.append(" + exp(-" + Math.abs(gamma) + " * " + valueString + " * " + valueString + ")");
			}
			first = false;
		}
		result.append("), " + degree + ")");
		return result.toString();
	}
	
	@Override
	public String toString() {
		return "Anova Kernel with" + Tools.getLineSeparator() +
			"  gamma: " + Tools.formatNumber(getGamma())  + Tools.getLineSeparator() +
			"  degree: " + degree;
	}
}