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package de.lmu.ifi.dbs.elki.evaluation.scores;
/*
This file is part of ELKI:
Environment for Developing KDD-Applications Supported by Index-Structures
Copyright (C) 2015
Ludwig-Maximilians-Universität München
Lehr- und Forschungseinheit für Datenbanksysteme
ELKI Development Team
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 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 Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
import de.lmu.ifi.dbs.elki.utilities.optionhandling.AbstractParameterizer;
/**
* Evaluate using the maximum F1 score.
*
* @author Erich Schubert
* @since 0.7.0
*/
public class MaximumF1Evaluation extends AbstractScoreEvaluation {
/**
* Static instance
*/
public static final MaximumF1Evaluation STATIC = new MaximumF1Evaluation();
@Override
public <I extends ScoreIter> double evaluate(Predicate<? super I> predicate, I iter) {
final int postot = predicate.numPositive();
int poscnt = 0, cnt = 0;
double maxf1 = 0.;
while(iter.valid()) {
// positive or negative match?
do {
if(predicate.test(iter)) {
++poscnt;
}
++cnt;
iter.advance();
} // Loop while tied:
while(iter.valid() && iter.tiedToPrevious());
// New F1 value:
double p = poscnt / (double) cnt, r = poscnt / (double) postot;
double f1 = 2. * p * r / (p + r);
if(f1 > maxf1) {
maxf1 = f1;
}
}
return maxf1;
}
@Override
public double expected(int pos, int all) {
return pos / (double) all;
}
/**
* Parameterization class.
*
* @author Erich Schubert
*
* @apiviz.exclude
*/
public static class Parameterizer extends AbstractParameterizer {
@Override
protected MaximumF1Evaluation makeInstance() {
return STATIC;
}
}
}
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