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1 ## Copyright (C) 2004 John Eaton, David Bateman |
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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 2, or (at your option) |
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8 ## 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, write to the Free |
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17 ## Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
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18 ## 02110-1301, USA. |
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19 |
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20 ## -*- texinfo -*- |
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21 ## @deftypefn {Function File} {@var{y} =} shiftdim (@var{x}, @var{n}) |
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22 ## @deftypefnx {Function File} {[@var{y}, @var{ns}] =} shiftdim (@var{x}) |
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23 ## Shifts the dimension of @var{x} by @var{n}, where @var{n} must be |
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24 ## an integer scalar. When @var{n} is positive, the dimensions of |
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25 ## @var{x} are shifted to the left, with the leading dimensions |
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26 ## circulated to the end. If @var{n} is negative, then the dimensions |
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27 ## of @var{x} are shifted to the right, with @var{n} leading singleton |
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28 ## dimensions added. |
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29 ## |
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30 ## Called with a single argument, @code{shiftdim}, removes the leading |
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31 ## singleton dimensions, returning the number of dimensions removed |
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32 ## in the second output argument @var{ns}. |
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33 ## |
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34 ## For example |
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35 ## |
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36 ## @example |
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37 ## @group |
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38 ## x = ones (1, 2, 3); |
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39 ## size (shiftdim (x, -1)) |
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40 ## @result{} [1, 1, 2, 3] |
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41 ## size (shiftdim (x, 1)) |
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42 ## @result{} [2, 3] |
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43 ## [b, ns] = shiftdim (x); |
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44 ## @result{} b = [1, 1, 1; 1, 1, 1] |
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45 ## @result{} ns = 1 |
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46 ## @end group |
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47 ## @end example |
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48 ## @seealso {reshape, permute, ipermute, circshift, squeeze} |
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49 ## @end deftypefn |
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50 |
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51 function [y, ns] = shiftdim (x, n) |
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52 |
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53 if (nargin < 1 || nargin > 2) |
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54 print_usage (); |
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55 endif |
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56 |
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57 nd = ndims (x); |
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58 orig_dims = size (x); |
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59 |
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60 if (nargin == 1) |
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61 ## Find the first singleton dimension. |
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62 n = 0; |
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63 while (n < nd && orig_dims(n+1) == 1) |
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64 n++; |
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65 endwhile |
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66 endif |
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67 |
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68 if (! isscalar (n) || floor (n) != n) |
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69 error ("shiftdim: n must be a scalar integer"); |
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70 endif |
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71 |
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72 if (n >= nd) |
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73 n = rem (n, nd); |
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74 endif |
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75 |
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76 if (n < 0) |
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77 singleton_dims = ones (1, -n); |
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78 y = reshape (x, [singleton_dims, orig_dims]); |
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79 elseif (n > 0) |
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80 ## We need permute here instead of reshape to shift values in a |
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81 ## compatible way. |
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82 y = permute (x, [n+1:ndims(x) 1:n]); |
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83 else |
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84 y = x; |
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85 endif |
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86 |
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87 ns = n; |
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88 |
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89 endfunction |
