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.math3.distribution;
018    
019    import org.apache.commons.math3.exception.NotStrictlyPositiveException;
020    import org.apache.commons.math3.exception.util.LocalizedFormats;
021    import org.apache.commons.math3.random.RandomGenerator;
022    
023    /**
024     * Base class for multivariate probability distributions.
025     *
026     * @version $Id: AbstractMultivariateRealDistribution.java 1416643 2012-12-03 19:37:14Z tn $
027     * @since 3.1
028     */
029    public abstract class AbstractMultivariateRealDistribution
030        implements MultivariateRealDistribution {
031        /** RNG instance used to generate samples from the distribution. */
032        protected final RandomGenerator random;
033        /** The number of dimensions or columns in the multivariate distribution. */
034        private final int dimension;
035    
036        /**
037         * @param rng Random number generator.
038         * @param n Number of dimensions.
039         */
040        protected AbstractMultivariateRealDistribution(RandomGenerator rng,
041                                                       int n) {
042            random = rng;
043            dimension = n;
044        }
045    
046        /** {@inheritDoc} */
047        public void reseedRandomGenerator(long seed) {
048            random.setSeed(seed);
049        }
050    
051        /** {@inheritDoc} */
052        public int getDimension() {
053            return dimension;
054        }
055    
056        /** {@inheritDoc} */
057        public abstract double[] sample();
058    
059        /** {@inheritDoc} */
060        public double[][] sample(final int sampleSize) {
061            if (sampleSize <= 0) {
062                throw new NotStrictlyPositiveException(LocalizedFormats.NUMBER_OF_SAMPLES,
063                                                       sampleSize);
064            }
065            final double[][] out = new double[sampleSize][dimension];
066            for (int i = 0; i < sampleSize; i++) {
067                out[i] = sample();
068            }
069            return out;
070        }
071    }