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 org.apache.commons.math.MathException;
19:
20: /**
21: * Base interface for probability distributions.
22: *
23: * @version $Revision: 155427 $ $Date: 2005-02-26 06:11:52 -0700 (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 ≤ X ≤ 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)
54: throws MathException;
55: }
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