    001    /*
    002     * Licensed to the Apache Software Foundation (ASF) under one or more
    003     * contributor license agreements.  See the NOTICE file distributed with
    004     * this work for additional information regarding copyright ownership.
    005     * The ASF licenses this file to You under the Apache License, Version 2.0
    006     * (the "License"); you may not use this file except in compliance with
    007     * the License.  You may obtain a copy of the License at
    008     *
    009     *      http://www.apache.org/licenses/LICENSE-2.0
    010     *
    011     * Unless required by applicable law or agreed to in writing, software
    012     * distributed under the License is distributed on an "AS IS" BASIS,
    013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014     * See the License for the specific language governing permissions and
    015     * limitations under the License.
    016     */
    017
    018    package org.apache.commons.math.linear;
    019
    020
    021    /**
    022     * An interface to classes that implement an algorithm to calculate the
    023     * QR-decomposition of a real matrix.
    024     * <p>This interface is based on the class with similar name from the
    025     * <a href="http://math.nist.gov/javanumerics/jama/">JAMA</a> library, with the
    026     * following changes:</p>
    027     * <ul>
    028     *   <li>a {@link #getQT() getQT} method has been added,</li>
    029     *   <li>the <code>solve</code> and <code>isFullRank</code> methods have been replaced
    030     *   by a {@link #getSolver() getSolver} method and the equivalent methods provided by
    031     *   the returned {@link DecompositionSolver}.</li>
    032     * </ul>
    033     *
    034     * @see <a href="http://mathworld.wolfram.com/QRDecomposition.html">MathWorld</a>
    035     * @see <a href="http://en.wikipedia.org/wiki/QR_decomposition">Wikipedia</a>
    036     * @version $Revision: 826627 $ $Date: 2009-10-19 12:27:47 +0200 (lun. 19 oct. 2009) $
    037     * @since 1.2
    038     */
    039    public interface QRDecomposition {
    040
    041        /**
    042         * Returns the matrix R of the decomposition.
    043         * <p>R is an upper-triangular matrix</p>
    044         * @return the R matrix
    045         */
    046        RealMatrix getR();
    047
    048        /**
    049         * Returns the matrix Q of the decomposition.
    050         * <p>Q is an orthogonal matrix</p>
    051         * @return the Q matrix
    052         */
    053        RealMatrix getQ();
    054
    055        /**
    056         * Returns the transpose of the matrix Q of the decomposition.
    057         * <p>Q is an orthogonal matrix</p>
    058         * @return the Q matrix
    059         */
    060        RealMatrix getQT();
    061
    062        /**
    063         * Returns the Householder reflector vectors.
    064         * <p>H is a lower trapezoidal matrix whose columns represent
    065         * each successive Householder reflector vector. This matrix is used
    066         * to compute Q.</p>
    067         * @return a matrix containing the Householder reflector vectors
    068         */
    069        RealMatrix getH();
    070
    071        /**
    072         * Get a solver for finding the A &times; X = B solution in least square sense.
    073         * @return a solver
    074         */
    075        DecompositionSolver getSolver();
    076
    077    }