org.uncertml.distribution.continuous.GammaDistribution.java Source code

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Here is the source code for org.uncertml.distribution.continuous.GammaDistribution.java

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/**
 * Copyright 2014 52North Initiative for Geospatial Open Source Software GmbH
 *
 * 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.uncertml.distribution.continuous;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import org.apache.commons.lang.ArrayUtils;

import org.uncertml.util.Validate;

/**
 * Class representing the gamma distribution with parameters shape and scale.
 * 
 * {@URL https://wiki.aston.ac.uk/foswiki/bin/view/UncertWeb/Gamma}
 * 
 * @author Matthew Williams
 * @version 2.0
 */
public class GammaDistribution implements IContinuousDistribution {

    private List<Double> shape;
    private List<Double> scale;

    /**
     * Constructor that takes a single shape and scale parameter.
     * 
     * @param shape the shape parameter
     * @param scale the scale parameter
     */
    public GammaDistribution(double shape, double scale) {
        this(new double[] { shape }, new double[] { scale });
    }

    /**
     * Constructor that takes an array of doubles for shape and scale parameters.
     * Each shape and scale pair represents a unique gamma distribution. This is 
     * in line with the UncertML syntax whereby a collection of types can be 
     * represented by a single entity. Both arrays must be of equal length and 
     * contain no null elements.
     * 
     * @param shape an array of doubles representing the shape parameter of n
     * gamma distributions.
     * @param scale an array of doubles representing the scale parameter of n 
     * gamma distributions.
     */
    public GammaDistribution(double[] shape, double[] scale) {
        this(Arrays.asList(ArrayUtils.toObject(shape)), Arrays.asList(ArrayUtils.toObject(scale)));
    }

    /**
     * Constructor that takes a list of doubles for shape and scale parameters.
     * Each shape and scale pair represents a unique gamma distribution. This is 
     * in line with the UncertML syntax whereby a collection of types can be 
     * represented by a single entity. Both lists must be of equal length and 
     * contain no null elements.
     * 
     * @param shape a list of doubles representing the shape parameter of n
     * gamma distributions.
     * @param scale a list of doubles representing the scale parameter of n 
     * gamma distributions.
     */
    public GammaDistribution(List<Double> shape, List<Double> scale) {
        Validate.notNull(shape);
        Validate.notNull(scale);
        Validate.noNullElements(shape);
        Validate.noNullElements(scale);
        Validate.allElementsGreaterThan(shape, 0.0);
        Validate.allElementsGreaterThan(scale, 0.0);
        Validate.allListsEqualLength(new List<?>[] { shape, scale });
        this.shape = new ArrayList<Double>(shape);
        this.scale = new ArrayList<Double>(scale);
    }

    /**
     * 
     * @return the scale parameter of each gamma distribution represented by this
     * object.
     */
    public List<Double> getScale() {
        return scale;
    }

    /**
     * 
     * @return the shape parameter of each gamma distribution represented by this
     * object.
     */
    public List<Double> getShape() {
        return shape;
    }

}