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
23 /**
24 * Base class for probability distributions.
25 *
26 * @version $Revision: 617953 $ $Date: 2008-02-02 22:54:00 -0700 (Sat, 02 Feb 2008) $
27 */
28 public abstract class AbstractDistribution
29 implements Distribution, Serializable {
30
31 /** Serializable version identifier */
32 private static final long serialVersionUID = -38038050983108802L;
33
34 /**
35 * Default constructor.
36 */
37 protected AbstractDistribution() {
38 super();
39 }
40
41 /**
42 * For a random variable X whose values are distributed according
43 * to this distribution, this method returns P(x0 ≤ X ≤ x1).
44 * <p>
45 * The default implementation uses the identity</p>
46 * <p>
47 * P(x0 ≤ X ≤ x1) = P(X ≤ x1) - P(X ≤ x0) </p>
48 *
49 * @param x0 the (inclusive) lower bound
50 * @param x1 the (inclusive) upper bound
51 * @return the probability that a random variable with this distribution
52 * will take a value between <code>x0</code> and <code>x1</code>,
53 * including the endpoints.
54 * @throws MathException if the cumulative probability can not be
55 * computed due to convergence or other numerical errors.
56 * @throws IllegalArgumentException if <code>x0 > x1</code>
57 */
58 public double cumulativeProbability(double x0, double x1)
59 throws MathException {
60 if (x0 > x1) {
61 throw new IllegalArgumentException
62 ("lower endpoint must be less than or equal to upper endpoint");
63 }
64 return cumulativeProbability(x1) - cumulativeProbability(x0);
65 }
66 }