001 /* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 package org.apache.commons.math.distribution; 018 019 import org.apache.commons.math.MathException; 020 021 /** 022 * Interface representing the Poisson Distribution. 023 * 024 * <p> 025 * References: 026 * <ul> 027 * <li><a href="http://mathworld.wolfram.com/PoissonDistribution.html"> 028 * Poisson distribution</a></li> 029 * </ul> 030 * </p> 031 * 032 * @version $Revision: 920852 $ $Date: 2010-03-09 07:53:44 -0500 (Tue, 09 Mar 2010) $ 033 */ 034 public interface PoissonDistribution extends IntegerDistribution { 035 036 /** 037 * Get the mean for the distribution. 038 * 039 * @return the mean for the distribution. 040 */ 041 double getMean(); 042 043 /** 044 * Set the mean for the distribution. 045 * The parameter value must be positive; otherwise an 046 * <code>IllegalArgument</code> is thrown. 047 * 048 * @param p the mean 049 * @throws IllegalArgumentException if p ≤ 0 050 * @deprecated as of v2.1 051 */ 052 @Deprecated 053 void setMean(double p); 054 055 /** 056 * Calculates the Poisson distribution function using a normal approximation. 057 * 058 * @param x the upper bound, inclusive 059 * @return the distribution function value calculated using a normal approximation 060 * @throws MathException if an error occurs computing the normal approximation 061 */ 062 double normalApproximateProbability(int x) throws MathException; 063 064 }