Mercurial > hg > octave-lyh
annotate scripts/general/diff.m @ 9015:06cebb6c5dde
Fix calculation of gradient for dims>2. Vector arguments are interpreted as
coordinate now. Tests added.
| author | Kai Habel <kai.habel@gmx.de> |
|---|---|
| date | Wed, 25 Mar 2009 14:33:44 -0400 |
| parents | eb63fbe60fab |
| children | 853f96e8008f |
| rev | line source |
|---|---|
| 8920 | 1 ## Copyright (C) 1995, 1996, 1999, 2000, 2002, 2004, 2005, 2006, 2007, |
| 2 ## 2008, 2009 Kurt Hornik | |
| 3426 | 3 ## |
| 3922 | 4 ## This file is part of Octave. |
| 5 ## | |
| 6 ## Octave is free software; you can redistribute it and/or modify it | |
| 7 ## under the terms of the GNU General Public License as published by | |
| 7016 | 8 ## the Free Software Foundation; either version 3 of the License, or (at |
| 9 ## your option) any later version. | |
| 3426 | 10 ## |
| 3922 | 11 ## Octave is distributed in the hope that it will be useful, but |
| 2539 | 12 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 3426 | 14 ## General Public License for more details. |
| 15 ## | |
| 2539 | 16 ## You should have received a copy of the GNU General Public License |
| 7016 | 17 ## along with Octave; see the file COPYING. If not, see |
| 18 ## <http://www.gnu.org/licenses/>. | |
| 2539 | 19 |
| 3369 | 20 ## -*- texinfo -*- |
| 4869 | 21 ## @deftypefn {Function File} {} diff (@var{x}, @var{k}, @var{dim}) |
| 3369 | 22 ## If @var{x} is a vector of length @var{n}, @code{diff (@var{x})} is the |
| 23 ## vector of first differences | |
| 24 ## @iftex | |
| 25 ## @tex | |
| 26 ## $x_2 - x_1, \ldots{}, x_n - x_{n-1}$. | |
| 27 ## @end tex | |
| 28 ## @end iftex | |
|
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29 ## @ifnottex |
| 3369 | 30 ## @var{x}(2) - @var{x}(1), @dots{}, @var{x}(n) - @var{x}(n-1). |
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31 ## @end ifnottex |
| 3426 | 32 ## |
| 3369 | 33 ## If @var{x} is a matrix, @code{diff (@var{x})} is the matrix of column |
| 4869 | 34 ## differences along the first non-singleton dimension. |
| 3426 | 35 ## |
| 3369 | 36 ## The second argument is optional. If supplied, @code{diff (@var{x}, |
| 37 ## @var{k})}, where @var{k} is a nonnegative integer, returns the | |
| 4869 | 38 ## @var{k}-th differences. It is possible that @var{k} is larger than |
| 39 ## then first non-singleton dimension of the matrix. In this case, | |
| 40 ## @code{diff} continues to take the differences along the next | |
| 41 ## non-singleton dimension. | |
| 42 ## | |
| 43 ## The dimension along which to take the difference can be explicitly | |
| 44 ## stated with the optional variable @var{dim}. In this case the | |
| 45 ## @var{k}-th order differences are calculated along this dimension. | |
| 46 ## In the case where @var{k} exceeds @code{size (@var{x}, @var{dim})} | |
| 47 ## then an empty matrix is returned. | |
| 3369 | 48 ## @end deftypefn |
| 2539 | 49 |
| 5428 | 50 ## Author: KH <Kurt.Hornik@wu-wien.ac.at> |
| 2539 | 51 ## Created: 2 February 1995 |
| 52 ## Adapted-By: jwe | |
| 53 | |
| 4869 | 54 function x = diff (x, k, dim) |
| 3426 | 55 |
| 4869 | 56 if (nargin < 1 || nargin > 3) |
| 6046 | 57 print_usage (); |
| 4869 | 58 endif |
| 59 | |
| 60 if (nargin < 2 || isempty(k)) | |
| 2539 | 61 k = 1; |
| 4869 | 62 else |
| 4030 | 63 if (! (isscalar (k) && k == round (k) && k >= 0)) |
| 2539 | 64 error ("diff: k must be a nonnegative integer"); |
| 65 elseif (k == 0) | |
| 66 return; | |
| 67 endif | |
| 4869 | 68 endif |
| 69 | |
| 70 nd = ndims (x); | |
| 71 sz = size (x); | |
| 72 if (nargin != 3) | |
| 73 %% Find the first non-singleton dimension | |
| 74 dim = 1; | |
| 75 while (dim < nd + 1 && sz (dim) == 1) | |
| 76 dim = dim + 1; | |
| 77 endwhile | |
| 78 if (dim > nd) | |
| 79 dim = 1; | |
| 80 endif | |
| 2539 | 81 else |
| 4869 | 82 if (! (isscalar (dim) && dim == round (dim)) && dim > 0 && |
| 83 dim < (nd + 1)) | |
| 84 error ("diff: dim must be an integer and valid dimension"); | |
| 85 endif | |
| 2539 | 86 endif |
| 3426 | 87 |
| 5443 | 88 if (ischar (x)) |
| 2539 | 89 error ("diff: symbolic differentiation not (yet) supported"); |
| 4869 | 90 endif |
| 91 | |
| 92 | |
| 93 if (nargin == 3) | |
| 94 if (sz (dim) <= k) | |
| 95 sz(dim) = 0; | |
| 96 x = zeros (sz); | |
| 2539 | 97 else |
| 4869 | 98 n = sz (dim); |
| 99 idx1 = cell (); | |
| 100 for i = 1:nd | |
| 7208 | 101 idx1{i} = 1:sz(i); |
| 2539 | 102 endfor |
| 4869 | 103 idx2 = idx1; |
| 104 for i = 1 : k; | |
| 7208 | 105 idx1{dim} = 2 : (n - i + 1); |
| 106 idx2{dim} = 1 : (n - i); | |
| 107 x = x(idx1{:}) - x(idx2{:}); | |
| 2539 | 108 endfor |
| 109 endif | |
| 110 else | |
| 4869 | 111 if (sum (sz - 1) < k) |
| 112 x = []; | |
| 113 else | |
| 114 idx1 = cell (); | |
| 115 for i = 1:nd | |
| 7208 | 116 idx1{i} = 1:sz(i); |
| 4869 | 117 endfor |
| 118 idx2 = idx1; | |
| 119 while (k) | |
| 120 n = sz (dim); | |
| 121 for i = 1 : min (k, n - 1) | |
| 7208 | 122 idx1{dim} = 2 : (n - i + 1); |
| 123 idx2{dim} = 1 : (n - i); | |
| 124 x = x(idx1{:}) - x(idx2{:}); | |
| 4869 | 125 endfor |
| 7208 | 126 idx1{dim} = idx2{dim} = 1; |
| 4869 | 127 k = k - min (k, n - 1); |
| 128 dim = dim + 1; | |
| 129 endwhile | |
| 130 endif | |
| 2539 | 131 endif |
| 132 | |
| 133 endfunction | |
| 7411 | 134 |
| 135 %!assert((diff ([1, 2, 3, 4]) == [1, 1, 1] | |
| 136 %! && diff ([1, 3, 7, 19], 2) == [2, 8] | |
| 137 %! && diff ([1, 2; 5, 4; 8, 7; 9, 6; 3, 1]) == [4, 2; 3, 3; 1, -1; -6, -5] | |
| 138 %! && diff ([1, 2; 5, 4; 8, 7; 9, 6; 3, 1], 3) == [-1, -5; -5, 0] | |
| 139 %! && isempty (diff (1)))); | |
| 140 | |
| 141 %!error diff ([1, 2; 3, 4], -1); | |
| 142 | |
| 143 %!error diff ("foo"); | |
| 144 | |
| 145 %!error diff (); | |
| 146 | |
| 147 %!error diff (1, 2, 3, 4); | |
| 148 |