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 */
017package org.apache.commons.math3.distribution;
018
019import org.apache.commons.math3.exception.NotStrictlyPositiveException;
020import org.apache.commons.math3.exception.util.LocalizedFormats;
021import org.apache.commons.math3.random.RandomGenerator;
022
023/**
024 * Base class for multivariate probability distributions.
025 *
026 * @since 3.1
027 */
028public abstract class AbstractMultivariateRealDistribution
029    implements MultivariateRealDistribution {
030    /** RNG instance used to generate samples from the distribution. */
031    protected final RandomGenerator random;
032    /** The number of dimensions or columns in the multivariate distribution. */
033    private final int dimension;
034
035    /**
036     * @param rng Random number generator.
037     * @param n Number of dimensions.
038     */
039    protected AbstractMultivariateRealDistribution(RandomGenerator rng,
040                                                   int n) {
041        random = rng;
042        dimension = n;
043    }
044
045    /** {@inheritDoc} */
046    public void reseedRandomGenerator(long seed) {
047        random.setSeed(seed);
048    }
049
050    /** {@inheritDoc} */
051    public int getDimension() {
052        return dimension;
053    }
054
055    /** {@inheritDoc} */
056    public abstract double[] sample();
057
058    /** {@inheritDoc} */
059    public double[][] sample(final int sampleSize) {
060        if (sampleSize <= 0) {
061            throw new NotStrictlyPositiveException(LocalizedFormats.NUMBER_OF_SAMPLES,
062                                                   sampleSize);
063        }
064        final double[][] out = new double[sampleSize][dimension];
065        for (int i = 0; i < sampleSize; i++) {
066            out[i] = sample();
067        }
068        return out;
069    }
070}