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Java > Open Source Codes > org > apache > commons > math > distribution > Distribution


1 /*
2  * Copyright 2004 The Apache Software Foundation.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
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 org.apache.commons.math.MathException;
19
20 /**
21  * Base interface for probability distributions.
22  *
23  * @version $Revision$ $Date: 2005-02-26 05:11:52 -0800 (Sat, 26 Feb 2005) $
24  */
25 public interface Distribution {
26     /**
27      * For a random variable X whose values are distributed according
28      * to this distribution, this method returns P(X ≤ x). In other words,
29      * this method represents the (cumulative) distribution function, or
30      * CDF, for this distribution.
31      *
32      * @param x the value at which the distribution function is evaluated.
33      * @return the probability that a random variable with this
34      * distribution takes a value less than or equal to <code>x</code>
35      * @throws MathException if the cumulative probability can not be
36      * computed due to convergence or other numerical errors.
37      */
38     double cumulativeProbability(double x) throws MathException;
39     
40     /**
41      * For a random variable X whose values are distributed according
42      * to this distribution, this method returns P(x0 &le; X &le; x1).
43      *
44      * @param x0 the (inclusive) lower bound
45      * @param x1 the (inclusive) upper bound
46      * @return the probability that a random variable with this distribution
47      * will take a value between <code>x0</code> and <code>x1</code>,
48      * including the endpoints
49      * @throws MathException if the cumulative probability can not be
50      * computed due to convergence or other numerical errors.
51      * @throws IllegalArgumentException if <code>x0 > x1</code>
52      */
53     double cumulativeProbability(double x0, double x1) throws MathException;
54 }
55
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