/*
* PoissonPartitionLikelihood.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.evomodel.arg;
import dr.inference.model.Model;
import dr.inference.model.Variable;
import dr.inference.model.Variable.ChangeType;
import dr.inferencexml.distribution.PriorParsers;
import dr.math.MathUtils;
import dr.math.Poisson;
import dr.math.distributions.PoissonDistribution;
import dr.xml.*;
import jebl.math.Binomial;
public class PoissonPartitionLikelihood extends ARGPartitionLikelihood {
public static final String POISSON_PARTITION_LIKELIHOOD = "poissonPartitionLikelihood";
PoissonDistribution pd;
double mean;
public PoissonPartitionLikelihood(String id, ARGModel arg, double mean) {
super(id, arg);
pd = new PoissonDistribution(mean);
this.mean = mean;
}
public double getLogLikelihood(double[] partition) {
if ((getNumberOfPartitionsMinusOne() + 1) % 2 == 0) {
return getEvenLogLikelihood(partition);
}
return getOddLogLikelihood(partition);
}
private double getEvenLogLikelihood(double[] partition) {
int numberOfZeros = 0;
int numberOfOnes = 0;
for (double d : partition) {
assert d == 0.0 || d == 1.0;
if (d == 0.0)
numberOfZeros++;
else
numberOfOnes++;
}
double poissonValue = (double) Math.min(numberOfZeros, numberOfOnes);
double logLike = pd.logPdf(poissonValue);
if (poissonValue < partition.length / 2) {
return logLike - Math.log(Binomial.choose(partition.length, poissonValue));
} else {
return logLike - Math.log(Binomial.choose(partition.length - 1, poissonValue));
}
}
private double getOddLogLikelihood(double[] partition) {
int numberOfZeros = 0;
int numberOfOnes = 0;
for (double d : partition) {
assert d == 0.0 || d == 1.0;
if (d == 0.0)
numberOfZeros++;
else
numberOfOnes++;
}
double poissonValue = (double) Math.min(numberOfZeros, numberOfOnes);
return pd.logPdf(poissonValue) -
Math.log(Binomial.choose(partition.length, poissonValue));
}
public double[] generatePartition() {
int lengthDividedByTwo = (getNumberOfPartitionsMinusOne() + 1) / 2;
int value = 0;
while (value < 1 || value > lengthDividedByTwo) {
value = Poisson.nextPoisson(mean);
}
int[] x = new int[getNumberOfPartitionsMinusOne() + 1];
for (int i = 0; i < value; i++) {
x[i] = 1;
}
MathUtils.permute(x);
if (x[0] == 1) {
for (int i = 0; i < x.length; i++) {
if (x[i] == 1) {
x[i] = 0;
} else {
x[i] = 1;
}
}
}
double[] rValue = new double[x.length];
for (int i = 0; i < rValue.length; i++) {
rValue[i] = x[i];
}
return rValue;
}
public static XMLObjectParser PARSER = new AbstractXMLObjectParser() {
public String getParserDescription() {
return null;
}
public Class getReturnType() {
return PoissonPartitionLikelihood.class;
}
public XMLSyntaxRule[] getSyntaxRules() {
return new XMLSyntaxRule[]{
AttributeRule.newDoubleRule(PriorParsers.MEAN, false),
new ElementRule(ARGModel.class, false),
};
}
public Object parseXMLObject(XMLObject xo) throws XMLParseException {
String id = "";
if (xo.hasId())
id = xo.getId();
double mean = xo.getDoubleAttribute(PriorParsers.MEAN);
ARGModel arg = (ARGModel) xo.getChild(ARGModel.class);
if (arg.isRecombinationPartitionType()) {
throw new XMLParseException(ARGModel.TREE_MODEL + " must be of type " + ARGModel.REASSORTMENT_PARTITION);
}
return new PoissonPartitionLikelihood(id, arg, mean);
}
public String getParserName() {
return POISSON_PARTITION_LIKELIHOOD;
}
};
protected void acceptState() {
//nothing to do
}
@Override
protected void handleModelChangedEvent(Model model, Object object, int index) {
//has no submodels
}
@Override
protected void handleVariableChangedEvent(Variable variable, int index,
ChangeType type) {
//has no parameters
}
@Override
protected void restoreState() {
//nothing to restore
}
@Override
protected void storeState() {
// nothing to store
}
}