/*
* 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.
*/
/*
* ErrorSetSize.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 ErrorSetSize loss function, which computes the size of
* the error set. The error set is composed of all possible label pairs,
* where one is relevant and the other is not, and which satisfy the condition
* that the relevant label is ranked lower than the irrelevant one.
*
* @author Grigorios Tsoumakas
* @version 2010.11.10
*/
public class ErrorSetSize extends RankingLossFunctionBase {
public String getName() {
return "ErrorSetSize";
}
@Override
public double computeLoss(int[] ranking, boolean[] groundTruth) {
double ess = 0;
int numLabels = groundTruth.length;
List<Integer> relevant = new ArrayList<Integer>();
List<Integer> irrelevant = new ArrayList<Integer>();
for (int index = 0; index < numLabels; index++) {
if (groundTruth[index]) {
relevant.add(index);
} else {
irrelevant.add(index);
}
}
for (int rLabel : relevant) {
for (int irLabel : irrelevant) {
if (ranking[rLabel] > ranking[irLabel]) {
ess++;
}
}
}
return ess;
}
}