001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.commons.math.distribution;
018    
019    import org.apache.commons.math.MathException;
020    
021    /**
022     * Base interface for probability distributions.
023     *
024     * @version $Revision: 1054524 $ $Date: 2011-01-03 05:59:18 +0100 (lun. 03 janv. 2011) $
025     */
026    public interface Distribution {
027        /**
028         * For a random variable X whose values are distributed according
029         * to this distribution, this method returns P(X ≤ x).  In other words,
030         * this method represents the  (cumulative) distribution function, or
031         * CDF, for this distribution.
032         *
033         * @param x the value at which the distribution function is evaluated.
034         * @return the probability that a random variable with this
035         * distribution takes a value less than or equal to <code>x</code>
036         * @throws MathException if the cumulative probability can not be
037         * computed due to convergence or other numerical errors.
038         */
039        double cumulativeProbability(double x) throws MathException;
040    
041        /**
042         * For a random variable X whose values are distributed according
043         * to this distribution, this method returns P(x0 &le; X &le; x1).
044         *
045         * @param x0 the (inclusive) lower bound
046         * @param x1 the (inclusive) upper bound
047         * @return the probability that a random variable with this distribution
048         * will take a value between <code>x0</code> and <code>x1</code>,
049         * including the endpoints
050         * @throws MathException if the cumulative probability can not be
051         * computed due to convergence or other numerical errors.
052         * @throws IllegalArgumentException if <code>x0 > x1</code>
053         */
054        double cumulativeProbability(double x0, double x1) throws MathException;
055    
056    }