org.apache.commons.math.distribution.DistributionFactory.java Source code

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Here is the source code for org.apache.commons.math.distribution.DistributionFactory.java

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/*
 * Copyright 2003-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.math.distribution;

import org.apache.commons.discovery.tools.DiscoverClass;

/**
 * This factory provids the means to create common statistical distributions.
 * The following distributions are supported:
 * <ul>
 * <li>Binomial</li>
 * <li>Chi-Squared</li>
 * <li>Exponential</li>
 * <li>F</li>
 * <li>Gamma</li>
 * <li>HyperGeometric</li>
 * <li>Poisson</li>
 * <li>Normal</li>
 * <li>Student's t</li>
 * </ul>
 *
 * Common usage:<pre>
 * DistributionFactory factory = DistributionFactory.newInstance();
 *
 * // create a Chi-Square distribution with 5 degrees of freedom.
 * ChiSquaredDistribution chi = factory.createChiSquareDistribution(5.0);
 * </pre>
 *
 * @version $Revision: 1.22 $ $Date: 2004/11/07 03:32:48 $
 */
public abstract class DistributionFactory {
    /**
     * Default constructor.
     */
    protected DistributionFactory() {
        super();
    }

    /**
     * Create an instance of a <code>DistributionFactory</code>
     * @return a new factory. 
     */
    public static DistributionFactory newInstance() {
        DistributionFactory factory = null;
        try {
            DiscoverClass dc = new DiscoverClass();
            factory = (DistributionFactory) dc.newInstance(DistributionFactory.class,
                    "org.apache.commons.math.distribution.DistributionFactoryImpl");
        } catch (Throwable t) {
            return new DistributionFactoryImpl();
        }
        return factory;
    }

    /**
     * Create a binomial distribution with the given number of trials and
     * probability of success.
     * 
     * @param numberOfTrials the number of trials.
     * @param probabilityOfSuccess the probability of success
     * @return a new binomial distribution
     */
    public abstract BinomialDistribution createBinomialDistribution(int numberOfTrials,
            double probabilityOfSuccess);

    /**
     * Create a new chi-square distribution with the given degrees of freedom.
     * 
     * @param degreesOfFreedom degrees of freedom
     * @return a new chi-square distribution  
     */
    public abstract ChiSquaredDistribution createChiSquareDistribution(double degreesOfFreedom);

    /**
     * Create a new exponential distribution with the given degrees of freedom.
     * 
     * @param mean mean
     * @return a new exponential distribution  
     */
    public abstract ExponentialDistribution createExponentialDistribution(double mean);

    /**
     * Create a new F-distribution with the given degrees of freedom.
     * 
     * @param numeratorDegreesOfFreedom numerator degrees of freedom
     * @param denominatorDegreesOfFreedom denominator degrees of freedom
     * @return a new F-distribution 
     */
    public abstract FDistribution createFDistribution(double numeratorDegreesOfFreedom,
            double denominatorDegreesOfFreedom);

    /**
     * Create a new gamma distribution with the given shape and scale
     * parameters.
     * 
     * @param alpha the shape parameter
     * @param beta the scale parameter
     * 
     * @return a new gamma distribution  
     */
    public abstract GammaDistribution createGammaDistribution(double alpha, double beta);

    /**
     * Create a new t distribution with the given degrees of freedom.
     * 
     * @param degreesOfFreedom degrees of freedom
     * @return a new t distribution  
     */
    public abstract TDistribution createTDistribution(double degreesOfFreedom);

    /**
     * Create a new hypergeometric distribution with the given the population
     * size, the number of successes in the population, and the sample size.
     * 
     * @param populationSize the population size
     * @param numberOfSuccesses number of successes in the population
     * @param sampleSize the sample size
     * @return a new hypergeometric desitribution
     */
    public abstract HypergeometricDistribution createHypergeometricDistribution(int populationSize,
            int numberOfSuccesses, int sampleSize);

    /**
     * Create a new normal distribution with the given mean and standard
     * deviation.
      * 
     * @param mean the mean of the distribution
     * @param sd standard deviation
     * @return a new normal distribution  
     */
    public abstract NormalDistribution createNormalDistribution(double mean, double sd);

    /**
     * Create a new normal distribution with mean zero and standard
     * deviation one.
      * 
     * @return a new normal distribution.  
     */
    public abstract NormalDistribution createNormalDistribution();

    /**
     * Create a new Poisson distribution with poisson parameter lambda.
     * 
     * @param lambda poisson parameter
     * @return a new normal distribution.  
     */
    public abstract PoissonDistribution createPoissonDistribution(double lambda);
}