Mercurial > octave-antonio
annotate scripts/linear-algebra/rref.m @ 20160:03b9d17a2d95 stable
doc: Update more docstrings to have one sentence summary as first line.
Reviewed io, java, linear-algebra, prefs, and set script directories.
* scripts/io/beep.m, scripts/io/dlmwrite.m, scripts/io/importdata.m,
scripts/io/strread.m, scripts/io/textread.m, scripts/java/javaArray.m,
scripts/java/java_get.m, scripts/java/java_set.m, scripts/java/javaaddpath.m,
scripts/java/javachk.m, scripts/java/javaclasspath.m, scripts/java/javamem.m,
scripts/java/javarmpath.m, scripts/linear-algebra/bandwidth.m,
scripts/linear-algebra/commutation_matrix.m, scripts/linear-algebra/cond.m,
scripts/linear-algebra/condest.m, scripts/linear-algebra/cross.m,
scripts/linear-algebra/duplication_matrix.m, scripts/linear-algebra/expm.m,
scripts/linear-algebra/housh.m, scripts/linear-algebra/isdefinite.m,
scripts/linear-algebra/ishermitian.m, scripts/linear-algebra/issymmetric.m,
scripts/linear-algebra/istril.m, scripts/linear-algebra/istriu.m,
scripts/linear-algebra/krylov.m, scripts/linear-algebra/logm.m,
scripts/linear-algebra/normest.m, scripts/linear-algebra/null.m,
scripts/linear-algebra/onenormest.m, scripts/linear-algebra/orth.m,
scripts/linear-algebra/qzhess.m, scripts/linear-algebra/rank.m,
scripts/linear-algebra/rref.m, scripts/linear-algebra/vech.m,
scripts/path/matlabroot.m, scripts/prefs/addpref.m, scripts/prefs/getpref.m,
scripts/prefs/ispref.m, scripts/prefs/rmpref.m, scripts/prefs/setpref.m,
scripts/set/powerset.m, scripts/set/setdiff.m:
Update more docstrings to have one sentence summary as first line.
author | Rik <rik@octave.org> |
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date | Sun, 03 May 2015 15:36:23 -0700 |
parents | 9fc020886ae9 |
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1 ## Copyright (C) 2000-2015 Paul Kienzle |
5827 | 2 ## |
3 ## This file is part of Octave. | |
4 ## | |
5 ## Octave is free software; you can redistribute it and/or modify it | |
6 ## under the terms of the GNU General Public License as published by | |
7016 | 7 ## the Free Software Foundation; either version 3 of the License, or (at |
8 ## your option) any later version. | |
5827 | 9 ## |
10 ## Octave is distributed in the hope that it will be useful, but | |
11 ## WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 ## General Public License for more details. | |
14 ## | |
15 ## You should have received a copy of the GNU General Public License | |
7016 | 16 ## along with Octave; see the file COPYING. If not, see |
17 ## <http://www.gnu.org/licenses/>. | |
5827 | 18 |
19 ## -*- texinfo -*- | |
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20 ## @deftypefn {Function File} {} rref (@var{A}) |
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21 ## @deftypefnx {Function File} {} rref (@var{A}, @var{tol}) |
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22 ## @deftypefnx {Function File} {[@var{r}, @var{k}] =} rref (@dots{}) |
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23 ## Return the reduced row echelon form of @var{A}. |
5827 | 24 ## |
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25 ## @var{tol} defaults to |
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26 ## @code{eps * max (size (@var{A})) * norm (@var{A}, inf)}. |
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27 ## |
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28 ## The optional return argument @var{k} contains the vector of |
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29 ## "bound variables", which are those columns on which elimination has been |
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30 ## performed. |
5827 | 31 ## |
32 ## @end deftypefn | |
33 | |
34 ## Author: Paul Kienzle <pkienzle@users.sf.net> | |
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35 ## (based on an anonymous source from the public domain) |
5827 | 36 |
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37 function [A, k] = rref (A, tol) |
5827 | 38 |
39 if (nargin < 1 || nargin > 2) | |
40 print_usage (); | |
41 endif | |
42 | |
43 if (ndims (A) > 2) | |
44 error ("rref: expecting matrix argument"); | |
45 endif | |
46 | |
47 [rows, cols] = size (A); | |
48 | |
49 if (nargin < 2) | |
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50 if (isa (A, "single")) |
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51 tol = eps ("single") * max (rows, cols) * norm (A, inf ("single")); |
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52 else |
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53 tol = eps * max (rows, cols) * norm (A, inf); |
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54 endif |
5827 | 55 endif |
56 | |
57 used = zeros (1, cols); | |
58 r = 1; | |
59 for c = 1:cols | |
60 ## Find the pivot row | |
61 [m, pivot] = max (abs (A(r:rows,c))); | |
62 pivot = r + pivot - 1; | |
63 | |
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64 if (m <= tol) |
5827 | 65 ## Skip column c, making sure the approximately zero terms are |
66 ## actually zero. | |
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67 A(r:rows, c) = zeros (rows-r+1, 1); |
5827 | 68 else |
69 ## keep track of bound variables | |
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70 used(1, c) = 1; |
5827 | 71 |
72 ## Swap current row and pivot row | |
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73 A([pivot, r], c:cols) = A([r, pivot], c:cols); |
5827 | 74 |
75 ## Normalize pivot row | |
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76 A(r, c:cols) = A(r, c:cols) / A(r, c); |
5827 | 77 |
78 ## Eliminate the current column | |
79 ridx = [1:r-1, r+1:rows]; | |
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80 A(ridx, c:cols) = A(ridx, c:cols) - A(ridx, c) * A(r, c:cols); |
5827 | 81 |
82 ## Check if done | |
83 if (r++ == rows) | |
10549 | 84 break; |
5827 | 85 endif |
86 endif | |
87 endfor | |
88 k = find (used); | |
89 | |
90 endfunction | |
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91 |
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92 |
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93 %!test |
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94 %! a = [1]; |
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95 %! [r k] = rref (a); |
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96 %! assert (r, [1], 2e-8); |
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97 %! assert (k, [1], 2e-8); |
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98 |
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99 %!test |
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100 %! a = [1 3; 4 5]; |
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101 %! [r k] = rref (a); |
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102 %! assert (rank (a), rank (r), 2e-8); |
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103 %! assert (r, eye (2), 2e-8); |
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104 %! assert (k == [1, 2] || k == [2, 1]); |
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105 |
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106 %!test |
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107 %! a = [1 3; 4 5; 7 9]; |
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108 %! [r k] = rref (a); |
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109 %! assert (rank (a), rank (r), 2e-8); |
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110 %! assert (r, eye(3)(:,1:2), 2e-8); |
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111 %! assert (k, [1 2], 2e-8); |
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112 |
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113 %!test |
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114 %! a = [1 2 3; 2 4 6; 7 2 0]; |
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115 %! [r k] = rref (a); |
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116 %! assert (rank (a), rank (r), 2e-8); |
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117 %! assert (r, [1 0 (3-7/2); 0 1 (7/4); 0 0 0], 2e-8); |
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118 %! assert (k, [1 2], 2e-8); |
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119 |
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120 %!test |
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121 %! a = [1 2 1; 2 4 2.01; 2 4 2.1]; |
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122 %! tol = 0.02; |
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123 %! [r k] = rref (a, tol); |
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124 %! assert (rank (a, tol), rank (r, tol), 2e-8); |
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125 %! tol = 0.2; |
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126 %! [r k] = rref (a, tol); |
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127 %! assert (rank (a, tol), rank (r, tol), 2e-8); |
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128 |
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129 %!error rref (); |
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130 |