1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 package org.apache.commons.math.distribution; 18 19 import org.apache.commons.math.MathException; 20 21 /** 22 * Interface representing the Poisson Distribution. 23 * 24 * <p> 25 * References: 26 * <ul> 27 * <li><a href="http://mathworld.wolfram.com/PoissonDistribution.html"> 28 * Poisson distribution</a></li> 29 * </ul> 30 * </p> 31 * 32 * @version $Revision: 670469 $ $Date: 2008-06-23 04:01:38 -0400 (Mon, 23 Jun 2008) $ 33 */ 34 public interface PoissonDistribution extends IntegerDistribution { 35 36 /** 37 * Get the mean for the distribution. 38 * 39 * @return the mean for the distribution. 40 */ 41 public double getMean(); 42 43 /** 44 * Set the mean for the distribution. 45 * The parameter value must be positive; otherwise an 46 * <code>IllegalArgument</code> is thrown. 47 * 48 * @param p the mean 49 * @throws IllegalArgumentException if p ≤ 0 50 */ 51 public void setMean(double p); 52 53 /** 54 * Calculates the Poisson distribution function using a normal approximation. 55 * 56 * @param x the upper bound, inclusive 57 * @return the distribution function value calculated using a normal approximation 58 * @throws MathException if an error occurs computing the normal approximation 59 */ 60 public double normalApproximateProbability(int x) throws MathException; 61 }