/*
 *  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.similarity.nominal;

import com.rapidminer.example.Attribute;
import com.rapidminer.example.ExampleSet;
import com.rapidminer.operator.OperatorException;
import com.rapidminer.tools.math.similarity.DistanceMeasure;

/**
 * A distance measure for nominal values accounting a value of one if two values are unequal.
 * 
 * @author Sebastian Land, Michael Wurst
 */
public class NominalDistance extends DistanceMeasure {

    private static final long serialVersionUID = -1239573851325335924L;

    private boolean[] useAttribute;

    @Override
    public double calculateDistance(double[] value1, double[] value2) {
        double sum = 0.0;
        int counter = 0;

        for (int i = 0; i < value1.length; i++) {
            if (useAttribute == null || useAttribute[i]) {
                if ((!Double.isNaN(value1[i])) && (!Double.isNaN(value2[i]))) {
                    if (value1[i] != value2[i])
                        sum = sum + 1.0;
                    counter++;
                }
            }
        }

        if (counter > 0)
            return sum;
        else
            return Double.NaN;
    }

    @Override
    public double calculateSimilarity(double[] value1, double[] value2) {
        return -calculateDistance(value1, value2);
    }

    // checking for example set and valid attributes
    @Override
    public void init(ExampleSet exampleSet) throws OperatorException {
        super.init(exampleSet);
        this.useAttribute = new boolean[exampleSet.getAttributes().size()];
        int i = 0;
        for (Attribute attribute : exampleSet.getAttributes()) {
            if (attribute.isNominal())
                useAttribute[i] = true;
            i++;
        }
    }

    @Override
    public String toString() {
        return "Nominal distance";
    }
}