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.validation.cross;
031
032import java.util.Iterator;
033import java.util.List;
034
035import org.openimaj.data.dataset.ListBackedDataset;
036import org.openimaj.data.dataset.ListDataset;
037import org.openimaj.experiment.dataset.util.DatasetAdaptors;
038import org.openimaj.experiment.validation.DefaultValidationData;
039import org.openimaj.experiment.validation.ValidationData;
040import org.openimaj.util.list.AcceptingListView;
041import org.openimaj.util.list.SkippingListView;
042
043/**
044 * Leave-One-Out Cross Validation (LOOCV) with a {@link ListDataset}.
045 * The number of iterations performed by the iterator is equal
046 * to the number of data items.
047 * <p>
048 * Upon each iteration, the dataset is split into training
049 * and validation sets. The validation set will have exactly one
050 * instance. All remaining instances are placed in the training
051 * set. As the iterator progresses, every instance will be included
052 * in the validation set one time.
053 * 
054 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
055 *
056 * @param <INSTANCE> Type of instances
057 */
058public class LeaveOneOut<INSTANCE> implements CrossValidator<ListDataset<INSTANCE>> {
059        private class LeaveOneOutIterable implements CrossValidationIterable<ListDataset<INSTANCE>> {
060                private ListDataset<INSTANCE> dataset;
061                private List<INSTANCE> listView;
062
063                /**
064                 * Construct {@link LeaveOneOutIterable} on the given dataset.
065                 * @param dataset the dataset
066                 */
067                public LeaveOneOutIterable(ListDataset<INSTANCE> dataset) {
068                        this.dataset = dataset;
069                        this.listView = DatasetAdaptors.asList(dataset);
070                }
071
072                /**
073                 * Get the number of iterations that the {@link Iterator}
074                 * returned by {@link #iterator()} will perform.
075                 * 
076                 * @return the number of iterations that will be performed
077                 */
078                @Override
079                public int numberIterations() {
080                        return dataset.size();
081                }
082
083                @Override
084                public Iterator<ValidationData<ListDataset<INSTANCE>>> iterator() {
085                        return new Iterator<ValidationData<ListDataset<INSTANCE>>>() {
086                                int validationIndex = 0;
087
088                                @Override
089                                public boolean hasNext() {
090                                        return validationIndex < dataset.size();
091                                }
092
093                                @Override
094                                public ValidationData<ListDataset<INSTANCE>> next() {
095                                        ListDataset<INSTANCE> training = new ListBackedDataset<INSTANCE>(new SkippingListView<INSTANCE>(listView, validationIndex));
096                                        ListDataset<INSTANCE> validation = new ListBackedDataset<INSTANCE>(new AcceptingListView<INSTANCE>(listView, validationIndex));
097
098                                        validationIndex++;
099
100                                        return new DefaultValidationData<ListDataset<INSTANCE>>(training, validation);
101                                }
102
103                                @Override
104                                public void remove() {
105                                        throw new UnsupportedOperationException();
106                                }
107                        };
108                }
109        }
110
111        @Override
112        public CrossValidationIterable<ListDataset<INSTANCE>> createIterable(ListDataset<INSTANCE> data) {
113                return new LeaveOneOutIterable(data);
114        }
115        
116        @Override
117        public String toString() {
118                return "Leave-One-Out Cross Validation (LOOCV)";
119        }
120}