    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     * Interface representing the Poisson Distribution.
    023     *
    024     * <p>
    025     * References:
    026     * <ul>
    027     * <li><a href="http://mathworld.wolfram.com/PoissonDistribution.html">
    028     * Poisson distribution</a></li>
    029     * </ul>
    030     * </p>
    031     *
    032     * @version $Revision: 920852 $ $Date: 2010-03-09 13:53:44 +0100 (mar. 09 mars 2010) $
    033     */
    034    public interface PoissonDistribution extends IntegerDistribution {
    035
    036        /**
    037         * Get the mean for the distribution.
    038         *
    039         * @return the mean for the distribution.
    040         */
    041        double getMean();
    042
    043        /**
    044         * Set the mean for the distribution.
    045         * The parameter value must be positive; otherwise an
    046         * <code>IllegalArgument</code> is thrown.
    047         *
    048         * @param p the mean
    049         * @throws IllegalArgumentException if p &le; 0
    050         * @deprecated as of v2.1
    051         */
    052        @Deprecated
    053        void setMean(double p);
    054
    055        /**
    056         * Calculates the Poisson distribution function using a normal approximation.
    057         *
    058         * @param x the upper bound, inclusive
    059         * @return the distribution function value calculated using a normal approximation
    060         * @throws MathException if an error occurs computing the normal approximation
    061         */
    062        double normalApproximateProbability(int x) throws MathException;
    063
    064    }