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Diffstat (limited to 'elki/src/main/java/de/lmu/ifi/dbs/elki/distance/similarityfunction/kernel/SigmoidKernelFunction.java')
-rw-r--r-- | elki/src/main/java/de/lmu/ifi/dbs/elki/distance/similarityfunction/kernel/SigmoidKernelFunction.java | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/elki/src/main/java/de/lmu/ifi/dbs/elki/distance/similarityfunction/kernel/SigmoidKernelFunction.java b/elki/src/main/java/de/lmu/ifi/dbs/elki/distance/similarityfunction/kernel/SigmoidKernelFunction.java new file mode 100644 index 00000000..82eb5ea6 --- /dev/null +++ b/elki/src/main/java/de/lmu/ifi/dbs/elki/distance/similarityfunction/kernel/SigmoidKernelFunction.java @@ -0,0 +1,110 @@ +package de.lmu.ifi.dbs.elki.distance.similarityfunction.kernel; + +/* + 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.data.NumberVector; +import de.lmu.ifi.dbs.elki.distance.distancefunction.AbstractNumberVectorDistanceFunction; +import de.lmu.ifi.dbs.elki.distance.similarityfunction.AbstractVectorSimilarityFunction; +import de.lmu.ifi.dbs.elki.utilities.optionhandling.AbstractParameterizer; +import de.lmu.ifi.dbs.elki.utilities.optionhandling.OptionID; +import de.lmu.ifi.dbs.elki.utilities.optionhandling.parameterization.Parameterization; +import de.lmu.ifi.dbs.elki.utilities.optionhandling.parameters.DoubleParameter; + +/** + * Sigmoid kernel function (aka: hyperbolic tangent kernel, multilayer + * perceptron MLP kernel). + * + * @author Erich Schubert + */ +public class SigmoidKernelFunction extends AbstractVectorSimilarityFunction { + /** + * Scaling factor c, bias theta + */ + private final double c, theta; + + /** + * Constructor. + * + * @param c Scaling factor c. + * @param theta Bias parameter theta. + */ + public SigmoidKernelFunction(double c, double theta) { + super(); + this.c = c; + this.theta = theta; + } + + @Override + public double similarity(NumberVector o1, NumberVector o2) { + final int dim = AbstractNumberVectorDistanceFunction.dimensionality(o1, o2); + double sim = 0.; + for (int i = 0; i < dim; i++) { + final double v = o1.doubleValue(i) * o2.doubleValue(i); + sim += v; + } + return Math.tanh(c * sim + theta); + } + + /** + * Parameterization class. + * + * @author Erich Schubert + * + * @apiviz.exclude + */ + public static class Parameterizer extends AbstractParameterizer { + /** + * C parameter: scaling + */ + public static final OptionID C_ID = new OptionID("kernel.sigmoid.c", "Sigmoid c parameter (scaling)."); + + /** + * Theta parameter: bias + */ + public static final OptionID THETA_ID = new OptionID("kernel.sigmoid.theta", "Sigmoid theta parameter (bias)."); + + /** + * C parameter, theta parameter + */ + protected double c = 1., theta = 0.; + + @Override + protected void makeOptions(Parameterization config) { + super.makeOptions(config); + final DoubleParameter cP = new DoubleParameter(C_ID, 1.); + if (config.grab(cP)) { + c = cP.doubleValue(); + } + final DoubleParameter thetaP = new DoubleParameter(THETA_ID, 0.); + if (config.grab(thetaP)) { + theta = thetaP.doubleValue(); + } + } + + @Override + protected SigmoidKernelFunction makeInstance() { + return new SigmoidKernelFunction(c, theta); + } + } +} |