MultipleEvaluation.java

/*
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 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 General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/*
 *    MultipleEvaluation.java
 *    Copyright (C) 2009-2010 Aristotle University of Thessaloniki, Thessaloniki, Greece
 */
package mulan.evaluation;

import java.util.ArrayList;
import java.util.HashMap;
import mulan.evaluation.measure.Measure;

/**
 * Simple class that includes an array, whose elements are lists of evaluation
 * evaluations. Used to compute means and standard deviations of multiple
 * evaluations (e.g. cross-validation)
 * 
 * @author Grigorios Tsoumakas
 */
public class MultipleEvaluation {

    private ArrayList<Evaluation> evaluations;
    private HashMap<String, Double> mean;
    private HashMap<String, Double> standardDeviation;

    /**
     * Constructs a new object
     */
    public MultipleEvaluation() {
        evaluations = new ArrayList<Evaluation>();
    }

    /**
     * Constructs a new object with given array of evaluations and calculates
     * statistics
     *
     * @param someEvaluations
     */
    public MultipleEvaluation(Evaluation[] someEvaluations) {
        evaluations = new ArrayList<Evaluation>();
        for (Evaluation e : someEvaluations) {
            evaluations.add(e);
        }
        calculateStatistics();
    }

    /**
     * Computes mean and standard deviation of all evaluation measures
     */
    public void calculateStatistics() {
        int size = evaluations.size();
        HashMap<String, Double> sums = new HashMap<String, Double>();

        // calculate sums of measures
        for (int i = 0; i < evaluations.size(); i++) {
            for (Measure m : evaluations.get(i).getMeasures()) {
                double value = Double.NaN;
                try {
                    value = m.getValue();
                } catch (Exception ex) {
                }
                if (sums.containsKey(m.getName())) {
                    sums.put(m.getName(), sums.get(m.getName()) + value);
                } else {
                    sums.put(m.getName(), value);
                }
            }
        }
        mean = new HashMap<String, Double>();
        for (String measureName : sums.keySet()) {
            mean.put(measureName, sums.get(measureName) / size);
        }

        // calculate sums of squared differences from mean
        sums = new HashMap<String, Double>();


        for (int i = 0; i < evaluations.size(); i++) {
            for (Measure m : evaluations.get(i).getMeasures()) {
                double value = Double.NaN;
                try {
                    value = m.getValue();
                } catch (Exception ex) {
                }
                if (sums.containsKey(m.getName())) {
                    sums.put(m.getName(), sums.get(m.getName()) + Math.pow(value - mean.get(m.getName()), 2));
                } else {
                    sums.put(m.getName(), Math.pow(value - mean.get(m.getName()), 2));
                }
            }
        }
        standardDeviation = new HashMap<String, Double>();
        for (String measureName : sums.keySet()) {
            standardDeviation.put(measureName, Math.sqrt(sums.get(measureName) / size));
        }
    }

    /**
     * Adds an evaluation results to the list of evaluations
     *
     * @param evaluation an evaluation result
     */
    public void addEvaluation(Evaluation evaluation) {
        evaluations.add(evaluation);
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        for (Measure m : evaluations.get(0).getMeasures()) {
            String measureName = m.getName();
            sb.append(measureName);
            sb.append(": ");
            sb.append(String.format("%.4f", mean.get(measureName)));
            sb.append("\u00B1");
            sb.append(String.format("%.4f", standardDeviation.get(measureName)));
            sb.append("\n");
        }
        return sb.toString();
    }

    /**
     * Returns the mean value of a measure
     *
     * @param measureName the name of the measure
     * @return the mean value of the measure
     */
    public double getMean(String measureName) {
        return mean.get(measureName);
    }
    
    /**
     * Returns the standard deviation value of a measure
     *
     * @param measureName the name of the measure
     * @return the standard deviation value of the measure
     */
    public double getStandardDeviation(String measureName) {
        return standardDeviation.get(measureName);
    }

    /**
     * Returns a CSV string representation of the results
     *
     * @return a CSV string representation of the results
     */
    public String toCSV() {
        StringBuilder sb = new StringBuilder();
        for (Measure m : evaluations.get(0).getMeasures()) {
            String measureName = m.getName();
            sb.append(String.format("%.4f", mean.get(measureName)));
            sb.append("\u00B1");
            sb.append(String.format("%.4f", standardDeviation.get(measureName)));
            sb.append(";");
        }
        return sb.toString();
    }
}