es.uam.eps.ir.ranksys.metrics.basic.Precision 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.rel.RelevanceModel;
import es.uam.eps.ir.ranksys.core.Recommendation;
import es.uam.eps.ir.ranksys.metrics.AbstractRecommendationMetric;
import es.uam.eps.ir.ranksys.metrics.rel.RelevanceModel.UserRelevanceModel;
import org.ranksys.core.util.tuples.Tuple2od;
/**
* Precision metric: proportion of relevant items in a recommendation list.
*
* @author Saúl Vargas ([email protected])
* @author Pablo Castells ([email protected])
*
* @param type of the users
* @param type of the items
*/
public class Precision extends AbstractRecommendationMetric {
private final RelevanceModel relModel;
private final int cutoff;
/**
* Constructor.
*
* @param cutoff maximum length of recommended lists
* @param relModel relevance model
*/
public Precision(int cutoff, RelevanceModel relModel) {
this.relModel = relModel;
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) {
UserRelevanceModel userRelModel = relModel.getModel(recommendation.getUser());
return recommendation.getItems().stream()
.limit(cutoff)
.map(Tuple2od::v1)
.filter(userRelModel::isRelevant)
.count() / (double) cutoff;
}
}