    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 &le; 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    }