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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.core.Recommendation;
import es.uam.eps.ir.ranksys.metrics.AbstractSystemMetric;
import es.uam.eps.ir.ranksys.metrics.RecommendationMetric;
import es.uam.eps.ir.ranksys.metrics.SystemMetric;
/**
* Average of a recommendation metric: system metric based on the arithmetic mean of a recommendation metric for a set of users' recommendations.
*
* @author Saúl Vargas ([email protected])
* @author Pablo Castells ([email protected])
*
* @param type of the users
* @param type of the items
*/
public class AverageRecommendationMetric extends AbstractSystemMetric {
private final RecommendationMetric metric;
private double sum;
private int numUsers;
private final boolean allUsers;
private final boolean ignoreNaN;
/**
* Constructor in which the number of users of the recommendation metric to be averaged is specified. Recommendations returning NaN or missing recommendations are treated as zeros to the average.
*
* @param metric recommendation metric to be averaged
* @param numUsers number of expected users' recommendations
*/
public AverageRecommendationMetric(RecommendationMetric metric, int numUsers) {
this.metric = metric;
this.sum = 0;
this.numUsers = numUsers;
this.allUsers = true;
this.ignoreNaN = false;
}
/**
* Constructor in which the average is calculated for all the recommendations added during the calculation.
*
* @param metric recommendation metric to be averaged
* @param ignoreNaN ignore NaNs from the calculation of the average?
*/
public AverageRecommendationMetric(RecommendationMetric metric, boolean ignoreNaN) {
this.metric = metric;
this.sum = 0;
this.numUsers = 0;
this.allUsers = false;
this.ignoreNaN = ignoreNaN;
}
/**
* Adds the recommendation metric to the average and returns the user value.
*
* @param recommendation recommendation to be added
* @return results of the recommender metric
*/
public double addAndEvaluate(Recommendation recommendation) {
double v = metric.evaluate(recommendation);
if (!ignoreNaN || !Double.isNaN(v)) {
sum += v;
if (!allUsers) {
numUsers++;
}
}
return v;
}
@Override
public void add(Recommendation recommendation) {
addAndEvaluate(recommendation);
}
@Override
public void combine(SystemMetric other) {
sum += ((AverageRecommendationMetric) other).sum;
if (!allUsers) {
numUsers += ((AverageRecommendationMetric) other).numUsers;
}
}
@Override
public double evaluate() {
return sum / numUsers;
}
@Override
public void reset() {
this.sum = 0;
if (!allUsers) {
this.numUsers = 0;
}
}
}