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.knn;
031
032import org.openimaj.util.comparator.DistanceComparator;
033import org.openimaj.util.pair.IntFloatPair;
034
035/**
036 * Abstract base class for k-nearest-neighbour calculations with any form of
037 * object that can be compared with a {@link DistanceComparator}.
038 *
039 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
040 * @author Sina Samangooei (ss@ecs.soton.ac.uk)
041 *
042 * @param <T>
043 *            Type of object being compared.
044 */
045public abstract class ObjectNearestNeighbours<T> implements NearestNeighbours<T, float[], IntFloatPair> {
046        protected DistanceComparator<? super T> distance;
047
048        /**
049         * Construct with the given distance measure
050         *
051         * @param distance
052         *            the distance measure
053         */
054        public ObjectNearestNeighbours(final DistanceComparator<? super T> distance) {
055                this.distance = distance;
056        }
057
058        /**
059         * Static method to find a distance between a query vector and point.
060         *
061         * @param <T>
062         *            Type of object being compared.
063         * @param distance
064         *            the distance measure
065         * @param qu
066         *            The query vector.
067         * @param pnt
068         *            The point
069         * @return the distance
070         */
071        public static <T> float distanceFunc(final DistanceComparator<? super T> distance, final T qu, final T pnt)
072        {
073                if (distance.isDistance()) {
074                        return (float) distance.compare(qu, pnt);
075                } else {
076                        return -(float) distance.compare(qu, pnt);
077                }
078        }
079
080        /**
081         * Get the distance comparator
082         *
083         * @return the distance comparator
084         */
085        public DistanceComparator<? super T> distanceComparator() {
086                return this.distance;
087        }
088}