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Diffstat (limited to 'src/de/lmu/ifi/dbs/elki/math/statistics/kernelfunctions/TricubeKernelDensityFunction.java')
-rw-r--r-- | src/de/lmu/ifi/dbs/elki/math/statistics/kernelfunctions/TricubeKernelDensityFunction.java | 105 |
1 files changed, 105 insertions, 0 deletions
diff --git a/src/de/lmu/ifi/dbs/elki/math/statistics/kernelfunctions/TricubeKernelDensityFunction.java b/src/de/lmu/ifi/dbs/elki/math/statistics/kernelfunctions/TricubeKernelDensityFunction.java new file mode 100644 index 00000000..933207ed --- /dev/null +++ b/src/de/lmu/ifi/dbs/elki/math/statistics/kernelfunctions/TricubeKernelDensityFunction.java @@ -0,0 +1,105 @@ +package de.lmu.ifi.dbs.elki.math.statistics.kernelfunctions; + +/* + This file is part of ELKI: + Environment for Developing KDD-Applications Supported by Index-Structures + + Copyright (C) 2013 + 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; + +/** + * Tricube kernel density estimator. + * + * @author Erich Schubert + */ +public final class TricubeKernelDensityFunction implements KernelDensityFunction { + /** + * Static instance. + */ + public static final TricubeKernelDensityFunction KERNEL = new TricubeKernelDensityFunction(); + + /** + * Canonical bandwidth. + * + * Computed as (R / STDDEV^4)^(1/5) + */ + public static final double CANONICAL_BANDWIDTH = Math.pow(59049 / 1729, .2); + + /** + * Standard deviation. + */ + private static final double STDDEV = Math.sqrt(35. / 243.); + + /** + * R constant. + */ + private static final double R = 175. / 247.; + + /** + * Scaling factor. + */ + private final double SCALE = 70. / 81.; + + /** + * Private, empty constructor. Use the static instance! + */ + private TricubeKernelDensityFunction() { + // Nothing to do. + } + + @Override + public double density(double delta) { + if (delta >= 1.) { + return 0; + } + final double u = 1 - delta * delta * delta; + return SCALE * u * u * u; + } + + @Override + public double canonicalBandwidth() { + return CANONICAL_BANDWIDTH; + } + + @Override + public double standardDeviation() { + return STDDEV; + } + + @Override + public double getR() { + return R; + } + + /** + * Parameterization stub. + * + * @author Erich Schubert + * + * @apiviz.exclude + */ + public static class Parameterizer extends AbstractParameterizer { + @Override + protected TricubeKernelDensityFunction makeInstance() { + return KERNEL; + } + } +} |