001/**
002 * Copyright (c) 2011, The University of Southampton and the individual contributors.
003 * All rights reserved.
004 *
005 * Redistribution and use in source and binary forms, with or without modification,
006 * are permitted provided that the following conditions are met:
007 *
008 *   *  Redistributions of source code must retain the above copyright notice,
009 *      this list of conditions and the following disclaimer.
010 *
011 *   *  Redistributions in binary form must reproduce the above copyright notice,
012 *      this list of conditions and the following disclaimer in the documentation
013 *      and/or other materials provided with the distribution.
014 *
015 *   *  Neither the name of the University of Southampton nor the names of its
016 *      contributors may be used to endorse or promote products derived from this
017 *      software without specific prior written permission.
018 *
019 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
020 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
021 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
022 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
023 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
024 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
025 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
026 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
027 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
028 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
029 */
030package org.openimaj.experiment.dataset.sampling;
031
032import java.util.Collection;
033
034import org.openimaj.data.dataset.GroupedDataset;
035import org.openimaj.data.dataset.ListDataset;
036import org.openimaj.data.dataset.MapBackedDataset;
037
038/**
039 * Sampler that samples whole groups from a {@link GroupedDataset}. Groups are
040 * chosen by selecting pre-determined keys.
041 * 
042 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
043 * 
044 * @param <KEY>
045 *            Type of groups
046 * @param <INSTANCE>
047 *            Type of instances
048 */
049public class NamedGroupSampler<KEY, INSTANCE>
050                implements
051                Sampler<GroupedDataset<KEY, ? extends ListDataset<INSTANCE>, INSTANCE>>
052{
053        Collection<KEY> keys;
054
055        /**
056         * Construct the sample to extract the given groups.
057         * 
058         * @param keys
059         *            the group keys to sample.
060         */
061        public NamedGroupSampler(Collection<KEY> keys) {
062                this.keys = keys;
063        }
064
065        @Override
066        public GroupedDataset<KEY, ListDataset<INSTANCE>, INSTANCE> sample(
067                        GroupedDataset<KEY, ? extends ListDataset<INSTANCE>, INSTANCE> dataset)
068        {
069                final MapBackedDataset<KEY, ListDataset<INSTANCE>, INSTANCE> sample = new MapBackedDataset<KEY, ListDataset<INSTANCE>, INSTANCE>();
070
071                for (final KEY key : keys) {
072                        sample.add(key, dataset.get(key));
073                }
074
075                return sample;
076        }
077
078        /**
079         * Sample a dataset by selecting only the given group keys.
080         * 
081         * @param dataset
082         *            the dataset to sample
083         * @param keys
084         *            the group keys to sample.
085         * @return the sampled dataset
086         */
087        public static <KEY, INSTANCE> GroupedDataset<KEY, ListDataset<INSTANCE>, INSTANCE> sample(
088                        GroupedDataset<KEY, ? extends ListDataset<INSTANCE>, INSTANCE> dataset, Collection<KEY> keys)
089        {
090                return new NamedGroupSampler<KEY, INSTANCE>(keys).sample(dataset);
091        }
092}