org.matsim.contrib.socnetgen.sna.snowball.analysis.ObservedTransitivity.java Source code

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/* *********************************************************************** *
 * project: org.matsim.*
 * ObservedTransitivity.java
 *                                                                         *
 * *********************************************************************** *
 *                                                                         *
 * copyright       : (C) 2010 by the members listed in the COPYING,        *
 *                   LICENSE and WARRANTY file.                            *
 * email           : info at matsim dot org                                *
 *                                                                         *
 * *********************************************************************** *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *   See also COPYING, LICENSE and WARRANTY file                           *
 *                                                                         *
 * *********************************************************************** */
package org.matsim.contrib.socnetgen.sna.snowball.analysis;

import gnu.trove.iterator.TObjectDoubleIterator;
import gnu.trove.map.hash.TObjectDoubleHashMap;

import java.util.Collection;
import java.util.Set;

import org.apache.commons.math.stat.descriptive.DescriptiveStatistics;
import org.matsim.contrib.socnetgen.sna.graph.Graph;
import org.matsim.contrib.socnetgen.sna.graph.Vertex;
import org.matsim.contrib.socnetgen.sna.graph.analysis.Transitivity;
import org.matsim.contrib.socnetgen.sna.snowball.SampledGraph;
import org.matsim.contrib.socnetgen.sna.snowball.SampledVertex;

/**
 * A class that provides functionality to analyze triangular configurations in a
 * graph from a snowball sample.
 * 
 * @author illenberger
 * 
 */
public class ObservedTransitivity extends Transitivity {

    private static ObservedTransitivity instance;

    public static ObservedTransitivity getInstance() {
        if (instance == null) {
            instance = new ObservedTransitivity();
        }
        return instance;
    }

    /**
     * Calculates the local clustering coefficients for all sampled vertices.
     * 
     * @see {@link Transitivity#localClusteringCoefficients(Collection)}
     * 
     * @param a
     *            collection of sampled vertices.
     * @return a object-double map with all sampled vertices and their local
     *         clustering coefficient.
     */
    @SuppressWarnings("unchecked")
    @Override
    public <V extends Vertex> TObjectDoubleHashMap<V> localClusteringCoefficients(Collection<V> vertices) {
        return (TObjectDoubleHashMap<V>) super.localClusteringCoefficients(
                SnowballPartitions.<SampledVertex>createSampledPartition((Collection<SampledVertex>) vertices));
    }

    /**
     * Returns a descriptive statistics object containing the local clustering
     * coefficient of all sampled vertices that have been sampled up to and
     * including the next to last iteration.
     * 
     * @param vertices
     *            a set of sampled vertices
     * @return a descriptive statistics object.
     */
    @SuppressWarnings("unchecked")
    @Override
    public DescriptiveStatistics statistics(Set<? extends Vertex> vertices) {
        DescriptiveStatistics stats = new DescriptiveStatistics();
        int iteration = SnowballStatistics.getInstance().lastIteration((Set<? extends SampledVertex>) vertices);

        TObjectDoubleHashMap<? extends Vertex> coefficients = localClusteringCoefficients(vertices);
        TObjectDoubleIterator<? extends Vertex> it = coefficients.iterator();

        for (int i = 0; i < coefficients.size(); i++) {
            it.advance();
            if (((SampledVertex) it.key()).getIterationSampled() <= iteration - 1) {
                stats.addValue(it.value());
            }
        }

        return stats;
    }

    /**
     * Calculates the global clustering coefficient including only sampled
     * vertices.
     * 
     * @param graph
     *            a sampled graph
     * @return the global clustering coefficient.
     */
    public double globalClusteringCoefficient(Graph graph) {
        double n_tripples = 0;
        double n_triangles = 0;

        SampledGraph sampledGraph = (SampledGraph) graph;
        int iteration = SnowballStatistics.getInstance().lastIteration(sampledGraph.getVertices());

        for (SampledVertex v : sampledGraph.getVertices()) {
            if (v.isSampled() && v.getIterationSampled() < iteration) {
                int k = v.getNeighbours().size();
                if (k > 1) {
                    int n_2 = k * (k - 1) / 2;
                    double n_3 = countAdjacentEdges(v);

                    n_tripples += n_2;
                    n_triangles += n_3;
                }
            }
        }

        return n_triangles / n_tripples;
    }
}