bigtop-master/bigtop-data-generators/bigtop-samplers/src/main/java/org/apache/bigtop/datagenerators/samplers/pdfs/JointPDF.java
/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.bigtop.datagenerators.samplers.pdfs;

import java.util.List;

public class JointPDF<T> implements ProbabilityDensityFunction<T>
{

	double normalizationFactor;
	ProbabilityDensityFunction<T>[] pdfs;

	public JointPDF(List<T> data, ProbabilityDensityFunction<T> ... pdfs)
	{
		this.pdfs = pdfs;

		normalizationFactor = 0.0d;
		for(T datum : data)
		{
			double prob = 1.0;
			for(ProbabilityDensityFunction<T> pdf : pdfs)
				prob *= pdf.probability(datum);
			normalizationFactor += prob;
		}

	}

	public double probability(T datum)
	{
		double weight = 1.0;
		for(ProbabilityDensityFunction<T> pdf : pdfs)
			weight *= pdf.probability(datum);

		return weight / normalizationFactor;
	}
}
