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comparison scripts/polynomial/convn.m @ 7640:3398ce778b4b

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Added support for N-dimensional convolution
author sh@sh-laptop
date Tue, 25 Mar 2008 21:28:02 -0400
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children e7b999840056
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7639:b2fbb393a072 7640:3398ce778b4b
1 ## Copyright (C) 2008 SÃ?ren Hauberg
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
7 ## the Free Software Foundation; either version 3 of the License, or (at
8 ## your option) any later version.
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
16 ## along with Octave; see the file COPYING. If not, see
17 ## <http://www.gnu.org/licenses/>.
18
19 ## -*- texinfo -*-
20 ## @deftypefn {Function File} {@var{c} =} convn (@var{a}, @var{b}, @var{shape})
21 ## @math{N}-dimensional convolution of matrices @var{a} and @var{b}.
22 ##
23 ## The size of the output is determined by the @var{shape} argument.
24 ## This can be any of the following character strings:
25 ##
26 ## @table @asis
27 ## @item "full"
28 ## The full convolution result is returned. The size out of the output is
29 ## @code{size (@var{a}) + size (@var{b})-1}. This is the default behaviour.
30 ## @item "same"
31 ## The central part of the convolution result is returned. The size out of the
32 ## output is the same as @var{a}.
33 ## @item "valid"
34 ## The valid part of the convolution is returned. The size of the result is
35 ## @code{max (size (@var{a}) - size (@var{b})+1, 0)}.
36 ## @end table
37 ##
38 ## @seealso{conv, conv2}
39 ## @end deftypefn
40
41 function c = convn (a, b, shape = "full")
42
43 if (nargin < 2)
44 error ("convn: not enough input arguments");
45 endif
46
47 if (!ismatrix (a) || !ismatrix (b) || ndims (a) != ndims (b))
48 error ("convn: first and second arguments must be matrices of the same dimensionality");
49 endif
50
51 if (!ischar (shape))
52 error ("convn: third input argument must be a string");
53 endif
54
55 if (!any (strcmpi (shape, {"full", "same", "valid"})))
56 error ("convn: invalid shape argument: '%s'", shape);
57 endif
58
59 ## Should we swap 'a' and 'b'?
60 ## FIXME -- should we also swap in any of the non-full cases?
61 if (numel (b) > numel (a) && strcmpi (shape, "full"))
62 tmp = a;
63 a = b;
64 b = tmp;
65 endif
66
67 ## Pad A.
68 switch (lower (shape))
69 case "full"
70 a = pad (a, size (b)-1, size (b)-1);
71 case "same"
72 a = pad (a, floor ((size (b)-1)/2), ceil ((size (b)-1)/2));
73 endswitch
74
75 ## Perform convolution.
76 c = __convn__ (a, b);
77
78 endfunction
79
80 ## Helper function that performs the padding.
81 function a = pad (a, left, right)
82 cl = class (a);
83 for dim = 1:ndims (a)
84 l = r = size (a);
85 l(dim) = left(dim);
86 r(dim) = right(dim);
87 a = cat (dim, zeros (l, cl), a, zeros (r, cl));
88 endfor
89 endfunction