/*
* FuLiD.java
*
* Copyright (c) 2002-2015 Alexei Drummond, Andrew Rambaut and Marc Suchard
*
* This file is part of BEAST.
* See the NOTICE file distributed with this work for additional
* information regarding copyright ownership and licensing.
*
* BEAST is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* BEAST 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with BEAST; if not, write to the
* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301 USA
*/
package dr.app.treestat.statistics;
import dr.evolution.tree.NodeRef;
import dr.evolution.tree.Tree;
/**
* @author Alexei Drummond
*
* @version $Id: FuLiD.java,v 1.2 2005/09/28 13:50:56 rambaut Exp $
*/
public class FuLiD extends AbstractTreeSummaryStatistic {
private FuLiD() { }
public double[] getSummaryStatistic(Tree tree) {
double externalLength = 0.0;
double internalLength = 0.0;
int externalNodeCount = tree.getExternalNodeCount();
for (int i = 0; i < externalNodeCount; i++) {
NodeRef node = tree.getExternalNode(i);
NodeRef parent = tree.getParent(node);
externalLength += tree.getNodeHeight(parent) - tree.getNodeHeight(node);
}
int internalNodeCount = tree.getInternalNodeCount();
for (int i = 0; i < internalNodeCount; i++) {
NodeRef node = tree.getInternalNode(i);
if (!tree.isRoot(node)) {
NodeRef parent = tree.getParent(node);
internalLength += tree.getNodeHeight(parent) - tree.getNodeHeight(node);
}
}
int n = externalNodeCount;
double total = externalLength + internalLength;
// difference in expectations
double D = total - a(n)*externalLength;
// normalized
D /= Math.sqrt(u(n)*total + (v(n)*(total*total)));
return new double[] { D };
}
private double a(int n) {
double a = 0.0;
for (int k = 1; k < n; k++) {
a += 1/(double)k;
}
return a;
}
private double b(int n) {
double b = 0.0;
for (int k = 1; k < n; k++) {
b += 1/(double)(k*k);
}
return b;
}
private double c(int n) {
if (n==2) return 1.0;
double an = a(n);
double c = 2.0 * (n * an - 2.0 * (n - 1.0));
c /= (n-1)*(n-2);
return c;
}
private double v(int n) {
double an2 = a(n);
an2 *= an2;
double v = 1 + (an2/(b(n)+an2)) * (c(n)-((n+1)/(n-1)));
return v;
}
private double u(int n) {
return a(n) - 1 - v(n);
}
public String getSummaryStatisticName() { return FACTORY.getSummaryStatisticName(); }
public String getSummaryStatisticDescription() { return FACTORY.getSummaryStatisticDescription(); }
public String getSummaryStatisticReference() { return FACTORY.getSummaryStatisticReference(); }
public boolean allowsPolytomies() { return FACTORY.allowsPolytomies(); }
public boolean allowsNonultrametricTrees() { return FACTORY.allowsNonultrametricTrees(); }
public boolean allowsUnrootedTrees() { return FACTORY.allowsUnrootedTrees(); }
public SummaryStatisticDescription.Category getCategory() { return FACTORY.getCategory(); }
public static final TreeSummaryStatistic.Factory FACTORY = new TreeSummaryStatistic.Factory() {
public TreeSummaryStatistic createStatistic() {
return new FuLiD();
}
public String getSummaryStatisticName() {
return "Fu & Li's D";
}
public String getSummaryStatisticDescription() {
return "The normalized difference between total tree length and external branch tree length. " +
"Note that this implementation uses branch lengths rather than the counts of mutations (this " +
"has a nice side-effect of taking into account complex mutation models.)";
}
public String getSummaryStatisticReference() {
return "Fu & Li (1993)";
}
public boolean allowsPolytomies() { return false; }
public boolean allowsNonultrametricTrees() { return false; }
public boolean allowsUnrootedTrees() { return false; }
public SummaryStatisticDescription.Category getCategory() { return SummaryStatisticDescription.Category.POPULATION_GENETIC; }
};
}