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package de.lmu.ifi.dbs.elki.utilities.scaling.outlier;
/*
This file is part of ELKI:
Environment for Developing KDD-Applications Supported by Index-Structures
Copyright (C) 2012
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.database.ids.DBID;
import de.lmu.ifi.dbs.elki.database.ids.DBIDIter;
import de.lmu.ifi.dbs.elki.math.DoubleMinMax;
import de.lmu.ifi.dbs.elki.result.outlier.OutlierResult;
import de.lmu.ifi.dbs.elki.utilities.documentation.Reference;
/**
* Scaling function to invert values by computing -1 * Math.log(x)
*
* Useful for example for scaling
* {@link de.lmu.ifi.dbs.elki.algorithm.outlier.ABOD}, but see
* {@link MinusLogStandardDeviationScaling} and {@link MinusLogGammaScaling} for
* more advanced scalings for this algorithm.
*
* @author Erich Schubert
*/
@Reference(authors = "H.-P. Kriegel, P. Kröger, E. Schubert, A. Zimek", title = "Interpreting and Unifying Outlier Scores", booktitle = "Proc. 11th SIAM International Conference on Data Mining (SDM), Mesa, AZ, 2011", url = "http://siam.omnibooksonline.com/2011datamining/data/papers/018.pdf")
public class OutlierMinusLogScaling implements OutlierScalingFunction {
/**
* Maximum value seen, set by {@link #prepare}
*/
double max = 0.0;
/**
* Maximum -log value seen, set by {@link #prepare}
*/
double mlogmax;
/**
* Constructor, adhering to
* {@link de.lmu.ifi.dbs.elki.utilities.optionhandling.Parameterizable}
*/
public OutlierMinusLogScaling() {
super();
}
@Override
public double getScaled(double value) {
assert (max != 0) : "prepare() was not run prior to using the scaling function.";
return -Math.log(value / max) / mlogmax;
}
@Override
public double getMin() {
return 0.0;
}
@Override
public double getMax() {
return 1.0;
}
@Override
public void prepare(OutlierResult or) {
DoubleMinMax mm = new DoubleMinMax();
for(DBIDIter iditer = or.getScores().iterDBIDs(); iditer.valid(); iditer.advance()) {
DBID id = iditer.getDBID();
double val = or.getScores().get(id);
if(!Double.isNaN(val) && !Double.isInfinite(val)) {
mm.put(val);
}
}
max = mm.getMax();
mlogmax = -Math.log(mm.getMin() / max);
}
}
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