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 06:27:47 -0400 (Mon, 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 × X = B solution in least square sense. 073 * @return a solver 074 */ 075 DecompositionSolver getSolver(); 076 077 }