es.uam.eps.ir.ranksys.metrics.basic.AveragePrecision Maven / Gradle / Ivy
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RankSys module, providing interfaces and common components for defining metrics.
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/*
* Copyright (C) 2015 Information Retrieval Group at Universidad Autónoma
* de Madrid, http://ir.ii.uam.es
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*/
package es.uam.eps.ir.ranksys.metrics.basic;
import es.uam.eps.ir.ranksys.metrics.AbstractRecommendationMetric;
import es.uam.eps.ir.ranksys.core.Recommendation;
import es.uam.eps.ir.ranksys.metrics.rel.IdealRelevanceModel;
import es.uam.eps.ir.ranksys.metrics.rel.IdealRelevanceModel.UserIdealRelevanceModel;
import static java.lang.Math.min;
import org.ranksys.core.util.tuples.Tuple2od;
/**
* Average Precision: average of the precision at each recall level.
*
* @author Saúl Vargas ([email protected])
*
* @param type of the users
* @param type of the items
*/
public class AveragePrecision extends AbstractRecommendationMetric {
private final IdealRelevanceModel relModel;
private final int cutoff;
/**
* Constructor.
*
* @param cutoff cutoff of the metric
* @param relevanceModel relevance model
*/
public AveragePrecision(int cutoff, IdealRelevanceModel relevanceModel) {
super();
this.relModel = relevanceModel;
this.cutoff = cutoff;
}
/**
* Returns a score for the recommendation list.
*
* @param recommendation recommendation list
* @return score of the metric to the recommendation
*/
@Override
public double evaluate(Recommendation recommendation) {
UserIdealRelevanceModel userRelModel = relModel.getModel(recommendation.getUser());
double ap = 0;
int relCount = 0;
int rank = 0;
for (Tuple2od pair : recommendation.getItems()) {
rank++;
if (userRelModel.isRelevant(pair.v1)) {
relCount++;
ap += relCount / (double) rank;
}
if (rank == cutoff) {
break;
}
}
return ap / (double) min(cutoff, userRelModel.getRelevantItems().size());
}
}