mirror of https://github.com/jlizier/jidt
126 lines
4.3 KiB
Java
Executable File
126 lines
4.3 KiB
Java
Executable File
/*
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* Java Information Dynamics Toolkit (JIDT)
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* Copyright (C) 2012, Joseph T. Lizier
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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package infodynamics.measures.continuous.kraskov;
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import java.util.Calendar;
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import java.util.PriorityQueue;
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import infodynamics.measures.continuous.MultiInfoCalculator;
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import infodynamics.utils.MathsUtils;
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import infodynamics.utils.NeighbourNodeData;
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/**
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* <p>Computes the differential multi-information of two given multivariate
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* sets of
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* observations (implementing {@link MultiInfoCalculator}),
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* using Kraskov-Stoegbauer-Grassberger (KSG) estimation (see Kraskov et al., below),
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* <b>algorithm 1</b>.
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* Most of the functionality is defined by the parent class
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* {@link MultiInfoCalculatorKraskov}.</p>
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*
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* <p>Usage is as per the paradigm outlined for {@link MultiInfoCalculator},
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* and expanded on in {@link MultiInfoCalculatorKraskov}.
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* </p>
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*
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* <p><b>References:</b><br/>
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* <ul>
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* <li>Kraskov, A., Stoegbauer, H., Grassberger, P.,
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* <a href="http://dx.doi.org/10.1103/PhysRevE.69.066138">"Estimating mutual information"</a>,
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* Physical Review E 69, (2004) 066138.</li>
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* </ul>
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*
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* @author Joseph Lizier (<a href="joseph.lizier at gmail.com">email</a>,
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* <a href="http://lizier.me/joseph/">www</a>)
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* @author Ipek Özdemir
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*/
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public class MultiInfoCalculatorKraskov1
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extends MultiInfoCalculatorKraskov {
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public MultiInfoCalculatorKraskov1() {
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super();
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isAlgorithm1 = true;
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}
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@Override
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protected double[] partialComputeFromObservations(
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int startTimePoint, int numTimePoints, boolean returnLocals) throws Exception {
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double startTime = Calendar.getInstance().getTimeInMillis();
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double[] localMi = null;
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if (returnLocals) {
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localMi = new double[numTimePoints];
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}
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// Constants:
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double dimensionsMinus1TimesDiGammaN = (double) (dimensions - 1) * digammaN;
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// Count the average number of points within eps_x for each marginal x of each point
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double sumDiGammas = 0;
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double[] sumNMarginals = new double[dimensions];
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for (int t = startTimePoint; t < startTimePoint + numTimePoints; t++) {
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// Compute eps for this time step by
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// finding the kth closest neighbour for point t:
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PriorityQueue<NeighbourNodeData> nnPQ =
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kdTreeJoint.findKNearestNeighbours(k, t, dynCorrExclTime);
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// First element in the PQ is the kth NN,
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// and epsilon = kthNnData.distance
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NeighbourNodeData kthNnData = nnPQ.poll();
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// Count the number of points whose x distance is less
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// than kthNnData.distance, for each marginal variable x:
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int[] n_marginals = new int[dimensions];
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double thisSumDiGammas = 0;
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for (int d = 0; d < dimensions; d++) {
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n_marginals[d] =
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rangeSearchersInMarginals[d].countPointsStrictlyWithinR(
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t, kthNnData.distance, dynCorrExclTime);
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sumNMarginals[d] += n_marginals[d];
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// And take the digammas:
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thisSumDiGammas += MathsUtils.digamma(n_marginals[d]+1);
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}
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sumDiGammas += thisSumDiGammas;
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if (returnLocals) {
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localMi[t-startTimePoint] = digammaK - thisSumDiGammas +
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dimensionsMinus1TimesDiGammaN;
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}
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}
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if (debug) {
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Calendar rightNow2 = Calendar.getInstance();
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long endTime = rightNow2.getTimeInMillis();
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System.out.println("Subset " + startTimePoint + ":" +
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(startTimePoint + numTimePoints) + " Calculation time: " +
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((endTime - startTime)/1000.0) + " sec" );
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}
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// Select what to return:
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if (returnLocals) {
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return localMi;
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} else {
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double[] returnArray = new double[dimensions+1];
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returnArray[0] = sumDiGammas;
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System.arraycopy(sumNMarginals, 0, returnArray, 1, dimensions);
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return returnArray;
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}
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}
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}
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