/******************************************************************************* * GenPlay, Einstein Genome Analyzer * Copyright (C) 2009, 2014 Albert Einstein College of Medicine * * This program is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * This program 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 General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see <http://www.gnu.org/licenses/>. * Authors: Julien Lajugie <julien.lajugie@einstein.yu.edu> * Nicolas Fourel <nicolas.fourel@einstein.yu.edu> * Eric Bouhassira <eric.bouhassira@einstein.yu.edu> * * Website: <http://genplay.einstein.yu.edu> ******************************************************************************/ package edu.yu.einstein.genplay.core.stat; import java.io.Serializable; import java.util.HashMap; import edu.yu.einstein.genplay.exception.exceptions.InvalidFactorialParameterException; /** * Factorial * This class allow to calculate factorial logarithm. * * @author Nicolas Fourel */ public class Factorial implements Serializable { private static final long serialVersionUID = -5327997963998890691L; //Attribute to store factorial values with parameter k as index and the factorial value on the cell private static HashMap<Integer, Double> logFactorialStorage = new HashMap<Integer, Double>(); /** * logFactorial method * This method calculate the parameter factorial logarithm. * If the parameter factorial logarithm already exists, method return it directly. * If it doesn't exists it is calculate. * If it is equal to 0 the method return 1. * If it is negative the method throw to InvalidFactorialParameterException. * * @param n to calculate its factorial * @return the factorial logarithm of the input parameter * @throws InvalidFactorialParameterException */ public static double logFactorial (int n) throws InvalidFactorialParameterException { double result = 0.0; if (n == 0) { result = 1.0; } else if (logFactorialStorage.containsKey(n)) { result = logFactorialStorage.get(n); } else if (n > 0) { for (int i=1; i<=n; i++) { result += Math.log10(i); } logFactorialStorage.put(n, result); } else { throw new InvalidFactorialParameterException(); } return result; } }