Mercurial > hg > octave-nkf
annotate scripts/sparse/spdiags.m @ 10687:a8ce6bdecce5
Improve documentation strings.
| author | Rik <octave@nomad.inbox5.com> |
|---|---|
| date | Tue, 08 Jun 2010 20:22:38 -0700 |
| parents | 16f53d29049f |
| children | be55736a0783 |
| rev | line source |
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| 9245 | 1 ## Copyright (C) 2000, 2001, 2004, 2005, 2007, 2008, 2009 Paul Kienzle |
| 7016 | 2 ## |
| 3 ## This file is part of Octave. | |
| 5164 | 4 ## |
| 7016 | 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 | |
| 7 ## the Free Software Foundation; either version 3 of the License, or (at | |
| 8 ## your option) any later version. | |
| 5164 | 9 ## |
| 7016 | 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. | |
| 5164 | 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/>. | |
| 5164 | 18 |
| 19 ## -*- texinfo -*- | |
| 7144 | 20 ## @deftypefn {Function File} {[@var{b}, @var{c}] =} spdiags (@var{a}) |
| 21 ## @deftypefnx {Function File} {@var{b} =} spdiags (@var{a}, @var{c}) | |
| 22 ## @deftypefnx {Function File} {@var{b} =} spdiags (@var{v}, @var{c}, @var{a}) | |
| 23 ## @deftypefnx {Function File} {@var{b} =} spdiags (@var{v}, @var{c}, @var{m}, @var{n}) | |
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24 ## A generalization of the function @code{diag}. Called with a single |
| 5164 | 25 ## input argument, the non-zero diagonals @var{c} of @var{A} are extracted. |
| 26 ## With two arguments the diagonals to extract are given by the vector | |
| 27 ## @var{c}. | |
| 28 ## | |
| 29 ## The other two forms of @code{spdiags} modify the input matrix by | |
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30 ## replacing the diagonals. They use the columns of @var{v} to replace |
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31 ## the columns represented by the vector @var{c}. If the sparse matrix |
| 5164 | 32 ## @var{a} is defined then the diagonals of this matrix are replaced. |
| 33 ## Otherwise a matrix of @var{m} by @var{n} is created with the | |
| 34 ## diagonals given by @var{v}. | |
| 35 ## | |
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36 ## Negative values of @var{c} represent diagonals below the main |
| 5164 | 37 ## diagonal, and positive values of @var{c} diagonals above the main |
| 38 ## diagonal. | |
| 39 ## | |
| 40 ## For example | |
| 41 ## | |
| 42 ## @example | |
| 43 ## @group | |
| 44 ## spdiags (reshape (1:12, 4, 3), [-1 0 1], 5, 4) | |
| 45 ## @result{} 5 10 0 0 | |
| 46 ## 1 6 11 0 | |
| 47 ## 0 2 7 12 | |
| 48 ## 0 0 3 8 | |
| 49 ## 0 0 0 4 | |
| 50 ## @end group | |
| 51 ## @end example | |
| 52 ## | |
| 53 ## @end deftypefn | |
| 54 | |
| 5568 | 55 function [A, c] = spdiags (v, c, m, n) |
| 5164 | 56 |
| 6498 | 57 if (nargin == 1 || nargin == 2) |
| 58 ## extract nonzero diagonals of v into A,c | |
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59 [nr, nc] = size (v); |
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60 [i, j, v] = find (v); |
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61 |
| 6498 | 62 if (nargin == 1) |
| 63 ## c contains the active diagonals | |
| 64 c = unique (j-i); | |
| 5164 | 65 endif |
| 6498 | 66 ## FIXME: we can do this without a loop if we are clever |
| 67 offset = max (min (c, nc-nr), 0); | |
| 68 A = zeros (min (nr, nc), length (c)); | |
| 69 for k = 1:length (c) | |
| 70 idx = find (j-i == c(k)); | |
| 71 A(j(idx)-offset(k),k) = v(idx); | |
| 72 endfor | |
| 73 elseif (nargin == 3) | |
| 74 ## Replace specific diagonals c of m with v,c | |
| 75 [nr, nc] = size (m); | |
| 76 B = spdiags (m, c); | |
| 77 A = m - spdiags (B, c, nr, nc) + spdiags (v, c, nr, nc); | |
| 78 else | |
| 79 ## Create new matrix of size mxn using v,c | |
| 80 [j, i, v] = find (v); | |
| 81 offset = max (min (c(:), n-m), 0); | |
| 6524 | 82 j = j(:) + offset(i); |
| 6498 | 83 i = j-c(:)(i); |
| 84 idx = i > 0 & i <= m & j > 0 & j <= n; | |
| 85 A = sparse (i(idx), j(idx), v(idx), m, n); | |
| 86 endif | |
| 5164 | 87 |
| 88 endfunction |