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 java.io.Serializable;
20
21 import org.apache.commons.math.MathException;
22 import org.apache.commons.math.MathRuntimeException;
23
24 /**
25 * Base class for probability distributions.
26 *
27 * @version $Revision: 772119 $ $Date: 2009-05-06 05:43:28 -0400 (Wed, 06 May 2009) $
28 */
29 public abstract class AbstractDistribution
30 implements Distribution, Serializable {
31
32 /** Serializable version identifier */
33 private static final long serialVersionUID = -38038050983108802L;
34
35 /**
36 * Default constructor.
37 */
38 protected AbstractDistribution() {
39 super();
40 }
41
42 /**
43 * For a random variable X whose values are distributed according
44 * to this distribution, this method returns P(x0 ≤ X ≤ x1).
45 * <p>
46 * The default implementation uses the identity</p>
47 * <p>
48 * P(x0 ≤ X ≤ x1) = P(X ≤ x1) - P(X ≤ x0) </p>
49 *
50 * @param x0 the (inclusive) lower bound
51 * @param x1 the (inclusive) upper bound
52 * @return the probability that a random variable with this distribution
53 * will take a value between <code>x0</code> and <code>x1</code>,
54 * including the endpoints.
55 * @throws MathException if the cumulative probability can not be
56 * computed due to convergence or other numerical errors.
57 * @throws IllegalArgumentException if <code>x0 > x1</code>
58 */
59 public double cumulativeProbability(double x0, double x1)
60 throws MathException {
61 if (x0 > x1) {
62 throw MathRuntimeException.createIllegalArgumentException(
63 "lower endpoint ({0}) must be less than or equal to upper endpoint ({1})",
64 x0, x1);
65 }
66 return cumulativeProbability(x1) - cumulativeProbability(x0);
67 }
68 }