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.math.model.fit.residuals;
031
032import org.openimaj.math.model.Model;
033import org.openimaj.util.comparator.DistanceComparator;
034import org.openimaj.util.pair.IndependentPair;
035
036/**
037 * An implementation of a {@link ResidualCalculator} that uses a
038 * {@link DistanceComparator} to compute the error between the predicted and
039 * observed data point. In the case that the given {@link DistanceComparator} is
040 * a similarity measure, the similarities will be multiplied by -1 to ensure
041 * error increases with decreasing similarity.
042 * 
043 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
044 * 
045 * @param <I>
046 *            type of independent data
047 * @param <D>
048 *            type of dependent data
049 * @param <M>
050 *            type of model
051 */
052public class DistanceComparatorResidual<I, D, M extends Model<I, D>> extends AbstractResidualCalculator<I, D, M> {
053        protected DistanceComparator<D> comparator;
054        private int multiplier = 1;
055
056        /**
057         * Construct with the given {@link DistanceComparator}.
058         * 
059         * @param comparator
060         *            the {@link DistanceComparator}
061         */
062        public DistanceComparatorResidual(DistanceComparator<D> comparator) {
063                this.comparator = comparator;
064
065                if (!comparator.isDistance())
066                        this.multiplier = -1;
067        }
068
069        @Override
070        public double computeResidual(IndependentPair<I, D> data) {
071                final D predicted = model.predict(data.firstObject());
072
073                return multiplier * comparator.compare(data.getSecondObject(), predicted);
074        }
075}