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.matrix.algorithm.whitening;
031
032import org.openimaj.citation.annotation.Reference;
033import org.openimaj.citation.annotation.ReferenceType;
034
035/**
036 * Abstract base class for whitening transforms ("sphering"). Whitening
037 * transforms rescale data to remove correlations; more specifically the idea of
038 * whitening is that it completely removes the second-order information
039 * (correlations and (co)-variances) of the data.
040 *
041 * @author Jonathon Hare (jsh2@ecs.soton.ac.uk)
042 *
043 */
044@Reference(
045                type = ReferenceType.Book,
046                author = { "Hyvrinen, Aapo", "Hurri, Jarmo", "Hoyer, Patrick O." },
047                title = "Natural Image Statistics: A Probabilistic Approach to Early Computational Vision.",
048                year = "2009",
049                edition = "1st",
050                publisher = "Springer Publishing Company, Incorporated",
051                customData = {
052                                "isbn", "1848824904, 9781848824904"
053                })
054public abstract class WhiteningTransform {
055        /**
056         * Apply the whitening transform to the given vector.
057         *
058         * @param vector
059         *            the vector
060         * @return the whitened vector
061         */
062        public abstract double[] whiten(double[] vector);
063
064        /**
065         * Apply the whitening transform to the given vectors.
066         *
067         * @param vector
068         *            the vectors; one per row
069         * @return the whitened vector
070         */
071        public double[][] whiten(double[][] vector) {
072                final double[][] out = new double[vector.length][];
073                for (int i = 0; i < vector.length; i++) {
074                        out[i] = whiten(vector[i]);
075                }
076                return out;
077        }
078
079        /**
080         * Train the whitening transform with the given features.
081         *
082         * @param data
083         *            the data (one feature per row)
084         */
085        public abstract void train(double[][] data);
086}