source: branches/ralph/src/main/java/de/ugoe/cs/autoquest/tasktrees/alignment/pal/tree/UPGMATree.java @ 1577

// UPGMATree.java
//
// (c) 1999-2001 PAL Development Core Team
//
// This package may be distributed under the
// terms of the Lesser GNU General Public License (LGPL)

// Known bugs and limitations:
// - computational complexity O(numSeqs^3)
//   (this could be brought down to O(numSeqs^2)
//   but this needs more clever programming ...)


package de.ugoe.cs.autoquest.tasktrees.alignment.pal.tree;

import java.util.ArrayList;

import de.ugoe.cs.autoquest.tasktrees.alignment.algorithms.NumberSequence;
import de.ugoe.cs.autoquest.tasktrees.alignment.matrix.UPGMAMatrix;
import de.ugoe.cs.autoquest.tasktrees.alignment.pal.misc.Identifier;


/**
 * constructs a UPGMA tree from pairwise distances
 *
 * @version $Id: UPGMATree.java,v 1.9 2001/07/13 14:39:13 korbinian Exp $
 *
 * @author Korbinian Strimmer
 * @author Alexei Drummond
 */
public class UPGMATree extends SimpleTree
{
        //
        // Public stuff
        //      

        /**
         * constructor UPGMA tree
         * @param numberseqs 
         *
         * @param m distance matrix
         */
        public UPGMATree(ArrayList<NumberSequence> numberseqs, UPGMAMatrix m)
        {
                if (m.size() < 2)
                {
                        new IllegalArgumentException("LESS THAN 2 TAXA IN DISTANCE MATRIX");
                }
        
                this.numberseqs = numberseqs;
                init(m);

                while (true)
                {
                        findNextPair();
                        newBranchLengths();
                        
                        if (numClusters == 2)
                        {
                                break;
                        }
                        
                        newCluster();
                }
                
                finish();
                createNodeList();
        }


        //
        // Private stuff
        //
        private ArrayList<NumberSequence> numberseqs;
        private int numClusters;
        private int besti, abi;
        private int bestj, abj;
        private int[] alias;
        private double[][] distance;

        private double[] height;
        private int[] oc;

        private double getDist(int a, int b)
        {
                return distance[alias[a]][alias[b]];
        }
        
        private void init(UPGMAMatrix m)
        {
                numClusters = m.size();

                distance = new double[numClusters][numClusters];
                for (int i = 0; i < numClusters; i++)
                {
                        for (int j = 0; j < numClusters; j++)
                        {
                                distance[i][j] = m.get(i,j);
                        }
                }

                for (int i = 0; i < numClusters; i++)
                {
                        Node tmp = NodeFactory.createNode();
                        tmp.setIdentifier(new Identifier(Integer.toString(i)));
                        tmp.addSequence(numberseqs.get(i));
                        getRoot().addChild(tmp);
                }
                
                alias = new int[numClusters];
                for (int i = 0; i < numClusters; i++)
                {
                        alias[i] = i;
                }
                                
                height = new double[numClusters];
                oc = new int[numClusters];
                for (int i = 0; i < numClusters; i++)
                {
                        height[i] = 0.0;
                        oc[i] = 1;
                }
        }

        private void finish()
        {
                distance = null;                
        }

        private void findNextPair()
        {
                besti = 0;
                bestj = 1;
                double dmin = getDist(0, 1);
                for (int i = 0; i < numClusters-1; i++)
                {
                        for (int j = i+1; j < numClusters; j++)
                        {
                                if (getDist(i, j) < dmin)
                                {
                                        dmin = getDist(i, j);
                                        besti = i;
                                        bestj = j;
                                }
                        }
                }
                abi = alias[besti];
                abj = alias[bestj];
                //System.out.println("Found best pair: " + abi + "/" +abj + " - "+ besti+ "/"+bestj +" with distance " + dmin);
                
        }

        private void newBranchLengths()
        {
                double dij = getDist(besti, bestj);
                
                getRoot().getChild(besti).setBranchLength(dij/2.0-height[abi]);
                getRoot().getChild(bestj).setBranchLength(dij/2.0-height[abj]);
        }

        private void newCluster()
        {
                // Update distances
                for (int k = 0; k < numClusters; k++)
                {
                        if (k != besti && k != bestj)
                        {
                                int ak = alias[k];
                                double updated = updatedDistance(besti,bestj,k);
                                distance[ak][abi] = distance[abi][ak] = updated;
                        }
                }
                distance[abi][abi] = 0.0;

                // Update UPGMA variables
                height[abi] = getDist(besti, bestj)/2.0;
                oc[abi] += oc[abj];
                
                // Index besti now represent the new cluster
                getRoot().joinChildren(besti, bestj);
                
                // Update alias
                for (int i = bestj; i < numClusters-1; i++)
                {
                        alias[i] = alias[i+1];
                }
                
                numClusters--;
        }

        
        /**
         * compute updated distance between the new cluster (i,j)
         * to any other cluster k
         */
        private double updatedDistance(int i, int j, int k)
        {
                int ai = alias[i];
                int aj = alias[j];
                
                double ocsum = (double) (oc[ai]+oc[aj]);
                double idist = getDist(k,i);
                double jdist = getDist(k,j);
                //TODO: Dirty hack to deal with infinity, insert proper solution here
                if(Double.isInfinite(idist)) {
                        idist = 100;
                }
                if(Double.isInfinite(jdist)) {
                        jdist = 100;
                }
                
                return  (oc[ai]/ocsum)*idist+
                        (oc[aj]/ocsum)*jdist;
        }
}