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1 ## Copyright (C) 2008 S�?ren Hauberg |
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2 ## |
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3 ## This file is part of Octave. |
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4 ## |
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5 ## Octave is free software; you can redistribute it and/or modify it |
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6 ## under the terms of the GNU General Public License as published by |
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7 ## the Free Software Foundation; either version 3 of the License, or (at |
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8 ## your option) any later version. |
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9 ## |
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10 ## Octave is distributed in the hope that it will be useful, but |
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11 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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13 ## General Public License for more details. |
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14 ## |
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15 ## You should have received a copy of the GNU General Public License |
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16 ## along with Octave; see the file COPYING. If not, see |
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17 ## <http://www.gnu.org/licenses/>. |
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18 |
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19 ## -*- texinfo -*- |
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20 ## @deftypefn {Function File} {@var{c} =} convn (@var{a}, @var{b}, @var{shape}) |
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21 ## @math{N}-dimensional convolution of matrices @var{a} and @var{b}. |
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22 ## |
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23 ## The size of the output is determined by the @var{shape} argument. |
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24 ## This can be any of the following character strings: |
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25 ## |
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26 ## @table @asis |
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27 ## @item "full" |
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28 ## The full convolution result is returned. The size out of the output is |
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29 ## @code{size (@var{a}) + size (@var{b})-1}. This is the default behaviour. |
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30 ## @item "same" |
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31 ## The central part of the convolution result is returned. The size out of the |
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32 ## output is the same as @var{a}. |
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33 ## @item "valid" |
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34 ## The valid part of the convolution is returned. The size of the result is |
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35 ## @code{max (size (@var{a}) - size (@var{b})+1, 0)}. |
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36 ## @end table |
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37 ## |
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38 ## @seealso{conv, conv2} |
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39 ## @end deftypefn |
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40 |
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41 function c = convn (a, b, shape = "full") |
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42 |
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43 if (nargin < 2) |
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44 error ("convn: not enough input arguments"); |
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45 endif |
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46 |
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47 if (!ismatrix (a) || !ismatrix (b) || ndims (a) != ndims (b)) |
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48 error ("convn: first and second arguments must be matrices of the same dimensionality"); |
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49 endif |
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50 |
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51 if (!ischar (shape)) |
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52 error ("convn: third input argument must be a string"); |
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53 endif |
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54 |
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55 if (!any (strcmpi (shape, {"full", "same", "valid"}))) |
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56 error ("convn: invalid shape argument: '%s'", shape); |
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57 endif |
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58 |
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59 ## Should we swap 'a' and 'b'? |
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60 ## FIXME -- should we also swap in any of the non-full cases? |
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61 if (numel (b) > numel (a) && strcmpi (shape, "full")) |
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62 tmp = a; |
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63 a = b; |
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64 b = tmp; |
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65 endif |
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66 |
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67 ## Pad A. |
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68 switch (lower (shape)) |
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69 case "full" |
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70 a = pad (a, size (b)-1, size (b)-1); |
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71 case "same" |
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72 a = pad (a, floor ((size (b)-1)/2), ceil ((size (b)-1)/2)); |
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73 endswitch |
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74 |
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75 ## Perform convolution. |
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76 c = __convn__ (a, b); |
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77 |
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78 endfunction |
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79 |
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80 ## Helper function that performs the padding. |
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81 function a = pad (a, left, right) |
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82 cl = class (a); |
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83 for dim = 1:ndims (a) |
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84 l = r = size (a); |
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85 l(dim) = left(dim); |
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86 r(dim) = right(dim); |
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87 a = cat (dim, zeros (l, cl), a, zeros (r, cl)); |
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88 endfor |
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89 endfunction |
