01: /*
02: * Copyright 2004 The Apache Software Foundation.
03: *
04: * Licensed under the Apache License, Version 2.0 (the "License");
05: * you may not use this file except in compliance with the License.
06: * You may obtain a copy of the License at
07: *
08: * http://www.apache.org/licenses/LICENSE-2.0
09: *
10: * Unless required by applicable law or agreed to in writing, software
11: * distributed under the License is distributed on an "AS IS" BASIS,
12: * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13: * See the License for the specific language governing permissions and
14: * limitations under the License.
15: */
16: package org.apache.commons.math.distribution;
17:
18: import java.io.Serializable;
19:
20: import org.apache.commons.math.MathException;
21:
22: /**
23: * Base class for probability distributions.
24: *
25: * @version $Revision: 348519 $ $Date: 2005-11-23 12:12:18 -0700 (Wed, 23 Nov 2005) $
26: */
27: public abstract class AbstractDistribution implements Distribution,
28: Serializable {
29:
30: /** Serializable version identifier */
31: private static final long serialVersionUID = -38038050983108802L;
32:
33: /**
34: * Default constructor.
35: */
36: protected AbstractDistribution() {
37: super ();
38: }
39:
40: /**
41: * For a random variable X whose values are distributed according
42: * to this distribution, this method returns P(x0 ≤ X ≤ x1).
43: * <p>
44: * The default implementation uses the identity
45: * <p>
46: * P(x0 ≤ X ≤ x1) = P(X ≤ x1) - P(X ≤ x0)
47: *
48: * @param x0 the (inclusive) lower bound
49: * @param x1 the (inclusive) upper bound
50: * @return the probability that a random variable with this distribution
51: * will take a value between <code>x0</code> and <code>x1</code>,
52: * including the endpoints.
53: * @throws MathException if the cumulative probability can not be
54: * computed due to convergence or other numerical errors.
55: * @throws IllegalArgumentException if <code>x0 > x1</code>
56: */
57: public double cumulativeProbability(double x0, double x1)
58: throws MathException {
59: if (x0 > x1) {
60: throw new IllegalArgumentException(
61: "lower endpoint must be less than or equal to upper endpoint");
62: }
63: return cumulativeProbability(x1) - cumulativeProbability(x0);
64: }
65: }
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