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 java.io.Serializable;
020
021 import org.apache.commons.math.MathException;
022 import org.apache.commons.math.MathRuntimeException;
023
024 /**
025 * Base class for probability distributions.
026 *
027 * @version $Revision: 811685 $ $Date: 2009-09-05 13:36:48 -0400 (Sat, 05 Sep 2009) $
028 */
029 public abstract class AbstractDistribution
030 implements Distribution, Serializable {
031
032 /** Serializable version identifier */
033 private static final long serialVersionUID = -38038050983108802L;
034
035 /**
036 * Default constructor.
037 */
038 protected AbstractDistribution() {
039 super();
040 }
041
042 /**
043 * For a random variable X whose values are distributed according
044 * to this distribution, this method returns P(x0 ≤ X ≤ x1).
045 * <p>
046 * The default implementation uses the identity</p>
047 * <p>
048 * P(x0 ≤ X ≤ x1) = P(X ≤ x1) - P(X ≤ x0) </p>
049 *
050 * @param x0 the (inclusive) lower bound
051 * @param x1 the (inclusive) upper bound
052 * @return the probability that a random variable with this distribution
053 * will take a value between <code>x0</code> and <code>x1</code>,
054 * including the endpoints.
055 * @throws MathException if the cumulative probability can not be
056 * computed due to convergence or other numerical errors.
057 * @throws IllegalArgumentException if <code>x0 > x1</code>
058 */
059 public double cumulativeProbability(double x0, double x1)
060 throws MathException {
061 if (x0 > x1) {
062 throw MathRuntimeException.createIllegalArgumentException(
063 "lower endpoint ({0}) must be less than or equal to upper endpoint ({1})",
064 x0, x1);
065 }
066 return cumulativeProbability(x1) - cumulativeProbability(x0);
067 }
068 }