/*
* 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.
*/
/*
* OneMinusAveragePrecision.java
* Copyright (C) 2009-2010 Aristotle University of Thessaloniki, Thessaloniki, Greece
*/
package mulan.evaluation.loss;
import java.util.ArrayList;
import java.util.List;
/**
* Implementation of the average precision as loss function.
*
* @author Grigorios Tsoumakas
* @version 2010.12.14
*/
public class OneMinusAveragePrecision extends RankingLossFunctionBase {
public String getName() {
return "1 - AveragePrecision";
}
@Override
public double computeLoss(int[] ranking, boolean[] trueLabels) {
double avgP = 0;
int numLabels = trueLabels.length;
List<Integer> relevant = new ArrayList<Integer>();
for (int index = 0; index < numLabels; index++) {
if (trueLabels[index]) {
relevant.add(index);
}
}
if (relevant.size() != 0) {
for (int r : relevant) {
double rankedAbove = 0;
for (int rr : relevant) {
if (ranking[rr] <= ranking[r]) {
rankedAbove++;
}
}
avgP += (rankedAbove / ranking[r]);
}
avgP /= relevant.size();
}
return 1 - avgP;
}
}