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.math4.distribution;
018
019import org.apache.commons.math4.exception.NotStrictlyPositiveException;
020import org.apache.commons.math4.exception.util.LocalizedFormats;
021import org.apache.commons.rng.UniformRandomProvider;
022
023/**
024 * Base class for multivariate probability distributions.
025 *
026 * @since 3.1
027 */
028public abstract class AbstractMultivariateRealDistribution
029    implements MultivariateRealDistribution {
030    /** The number of dimensions or columns in the multivariate distribution. */
031    private final int dimension;
032
033    /**
034     * @param n Number of dimensions.
035     */
036    protected AbstractMultivariateRealDistribution(int n) {
037        dimension = n;
038    }
039
040    /** {@inheritDoc} */
041    @Override
042    public int getDimension() {
043        return dimension;
044    }
045
046    /** {@inheritDoc} */
047    @Override
048    public abstract Sampler createSampler(UniformRandomProvider rng);
049
050    /**
051     * Utility function for creating {@code n} vectors generated by the
052     * given {@code sampler}.
053     *
054     * @param n Number of samples.
055     * @param sampler Sampler.
056     * @return an array of size {@code n} whose elements are random vectors
057     * sampled from this distribution.
058     */
059    public static double[][] sample(int n,
060                                    MultivariateRealDistribution.Sampler sampler) {
061        if (n <= 0) {
062            throw new NotStrictlyPositiveException(LocalizedFormats.NUMBER_OF_SAMPLES,
063                                                   n);
064        }
065
066        final double[][] samples = new double[n][];
067        for (int i = 0; i < n; i++) {
068            samples[i] = sampler.sample();
069        }
070        return samples;
071    }
072}