content: /**
   * 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;
  	}
  }
  