Added statistical measures on community size distribution (requires o…

…rg.apache.commons.math).

src/org/graphstream/algorithm/measure/CommunityDistribution.java

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+/*
+ * This file is part of GraphStream.
+ * 
+ * GraphStream 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 3 of the License, or
+ * (at your option) any later version.
+ * 
+ * GraphStream 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 General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with GraphStream.  If not, see <http://www.gnu.org/licenses/>.
+ * 
+ * Project copyright 2006 - 2010
+ * 	Julien Baudry
+ * 	Antoine Dutot
+ * 	Yoann Pigné
+ * 	Guilhelm Savin
+ *
+ * This file is copyright 2010
+ *  Guillaume-Jean Herbiet
+ */
+package org.graphstream.algorithm.measure;
+
+import org.apache.commons.math.stat.descriptive.moment.*;
+
+/**
+ * Provides some statistical information on the size of current community
+ * assignment on the specified graph as it evolves.
+ * 
+ * @author Guillaume-Jean Herbiet
+ * 
+ */
+public class CommunityDistribution extends CommunityMeasure {
+
+	/**
+	 * Biggest community currently generated.
+	 */
+	protected Object biggestCommunity = null;
+
+	/**
+	 * Smallest community currently generated.
+	 */
+	protected Object smallestCommunity = null;
+
+	/**
+	 * Average size of the currently generated communities.
+	 */
+	protected float avgSize = 0;
+
+	/**
+	 * Standard deviation of the size of currently generated communities.
+	 */
+	protected float stdevSize = 0;
+
+	/**
+	 * New size distribution measure using the specified marker as attribute
+	 * name for the community assignment.
+	 * 
+	 * @param marker
+	 *            Attribute name for the community assignment.
+	 */
+	public CommunityDistribution(String marker) {
+		super(marker);
+	}
+
+	@Override
+	/**
+	 * Computes and update the statistical information on size distribution.
+	 * 
+	 * @complexity O(C), where C is the expected number of communities.
+	 */
+	public void compute() {
+		if (graphChanged) {
+			// Default measure is the number of communities
+			M = (float) communities.size();
+
+			// Update the smallest/biggest community
+			// and creates the size distribution
+			int maxSize = 0;
+			int minSize = Integer.MAX_VALUE;
+
+			double[] distribution = new double[(int) M];
+			int k = 0;
+			Mean mean = new Mean();
+			StandardDeviation stdev = new StandardDeviation();
+
+			for (Object c : communities.keySet()) {
+				distribution[k++] = (communities.get(c)).size();
+
+				if ((communities.get(c)).size() > maxSize) {
+					biggestCommunity = c;
+					maxSize = (communities.get(c)).size();
+				}
+				if ((communities.get(c)).size() < minSize) {
+					smallestCommunity = c;
+					minSize = (communities.get(c)).size();
+				}
+			}
+
+			// Compute the statistical moments
+			avgSize = (float) mean.evaluate(distribution);
+			stdevSize = (float) stdev.evaluate(distribution);
+
+			graphChanged = false;
+		}
+	}
+
+	/**
+	 * Get the number of communities
+	 * 
+	 * @return an int representing the current number of communities
+	 */
+	public int number() {
+		return (int) M;
+	}
+
+	/**
+	 * Get the biggest generated community
+	 * 
+	 * @return the biggest community
+	 */
+	public Object biggestCommunity() {
+		return biggestCommunity;
+	}
+
+	/**
+	 * Get the smallest generated community
+	 * 
+	 * @return the smallest community
+	 */
+	public Object smallestCommunity() {
+		return smallestCommunity;
+	}
+
+	/**
+	 * Get the maximum community size
+	 * 
+	 * @return an int reflecting the size of the biggest community
+	 */
+	public int maxCommunitySize() {
+		if (communities.get(biggestCommunity) == null)
+			return 0;
+		else
+			return (communities.get(biggestCommunity)).size();
+	}
+
+	/**
+	 * Get the minimum community size
+	 * 
+	 * @return an int reflecting the size of the smallest community
+	 */
+	public int minCommunitySize() {
+		if (communities.get(smallestCommunity) == null)
+			return 0;
+		else
+			return (communities.get(smallestCommunity)).size();
+	}
+
+	/**
+	 * Compute the average community size
+	 * 
+	 * @return Average community size
+	 */
+	public float average() {
+		return avgSize;
+	}
+
+	/**
+	 * Compute the standard deviation of the community size
+	 * 
+	 * @return Standard deviation of the community size
+	 */
+	public float stdev() {
+		return stdevSize;
+	}
+
+	/**
+	 * Updates the distribution information and returns a string for an easy
+	 * display of the results.
+	 * 
+	 * The string has the following format: [number of communities] [average
+	 * size] [stdev size] [min size] ([smallest community]) [max size] ([biggest
+	 * community])
+	 * 
+	 * @return a String containing all computed distribution information.
+	 */
+	public String toString() {
+		compute();
+		return (int) M + " " + avgSize + " " + stdevSize + " "
+				+ minCommunitySize() + " (" + smallestCommunity + ") "
+				+ maxCommunitySize() + " (" + biggestCommunity + ")";
+	}
+
+}