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 import org.apache.commons.math.exception.util.LocalizedFormats;
024
025 /**
026 * Base class for probability distributions.
027 *
028 * @version $Revision: 1054524 $ $Date: 2011-01-03 05:59:18 +0100 (lun. 03 janv. 2011) $
029 */
030 public abstract class AbstractDistribution
031 implements Distribution, Serializable {
032
033 /** Serializable version identifier */
034 private static final long serialVersionUID = -38038050983108802L;
035
036 /**
037 * Default constructor.
038 */
039 protected AbstractDistribution() {
040 super();
041 }
042
043 /**
044 * For a random variable X whose values are distributed according
045 * to this distribution, this method returns P(x0 ≤ X ≤ x1).
046 * <p>
047 * The default implementation uses the identity</p>
048 * <p>
049 * P(x0 ≤ X ≤ x1) = P(X ≤ x1) - P(X ≤ x0) </p>
050 *
051 * @param x0 the (inclusive) lower bound
052 * @param x1 the (inclusive) upper bound
053 * @return the probability that a random variable with this distribution
054 * will take a value between <code>x0</code> and <code>x1</code>,
055 * including the endpoints.
056 * @throws MathException if the cumulative probability can not be
057 * computed due to convergence or other numerical errors.
058 * @throws IllegalArgumentException if <code>x0 > x1</code>
059 */
060 public double cumulativeProbability(double x0, double x1)
061 throws MathException {
062 if (x0 > x1) {
063 throw MathRuntimeException.createIllegalArgumentException(
064 LocalizedFormats.LOWER_ENDPOINT_ABOVE_UPPER_ENDPOINT,
065 x0, x1);
066 }
067 return cumulativeProbability(x1) - cumulativeProbability(x0);
068 }
069 }