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 org.apache.commons.math.MathException;
20
21 /**
22 * Base interface for probability distributions.
23 *
24 * @version $Revision: 480440 $ $Date: 2006-11-29 00:14:12 -0700 (Wed, 29 Nov 2006) $
25 */
26 public interface Distribution {
27 /**
28 * For a random variable X whose values are distributed according
29 * to this distribution, this method returns P(X ≤ x). In other words,
30 * this method represents the (cumulative) distribution function, or
31 * CDF, for this distribution.
32 *
33 * @param x the value at which the distribution function is evaluated.
34 * @return the probability that a random variable with this
35 * distribution takes a value less than or equal to <code>x</code>
36 * @throws MathException if the cumulative probability can not be
37 * computed due to convergence or other numerical errors.
38 */
39 double cumulativeProbability(double x) throws MathException;
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 *
45 * @param x0 the (inclusive) lower bound
46 * @param x1 the (inclusive) upper bound
47 * @return the probability that a random variable with this distribution
48 * will take a value between <code>x0</code> and <code>x1</code>,
49 * including the endpoints
50 * @throws MathException if the cumulative probability can not be
51 * computed due to convergence or other numerical errors.
52 * @throws IllegalArgumentException if <code>x0 > x1</code>
53 */
54 double cumulativeProbability(double x0, double x1) throws MathException;
55 }