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annotate scripts/general/shiftdim.m @ 17508:9b2443f97a3e

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Merge the official development
author LYH <lyh.kernel@gmail.com>
date Thu, 26 Sep 2013 04:47:20 +0800
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72c96de7a403 maint: update copyright notices for 2012
John W. Eaton <jwe@octave.org>
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1 ## Copyright (C) 2004-2012 John Eaton and 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 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{y} =} shiftdim (@var{x}, @var{n})
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21 ## @deftypefnx {Function File} {[@var{y}, @var{ns}] =} shiftdim (@var{x})
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22 ## Shift the dimensions of @var{x} by @var{n}, where @var{n} must be
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23 ## an integer scalar. When @var{n} is positive, the dimensions of
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24 ## @var{x} are shifted to the left, with the leading dimensions
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25 ## circulated to the end. If @var{n} is negative, then the dimensions
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26 ## of @var{x} are shifted to the right, with @var{n} leading singleton
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27 ## dimensions added.
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28 ##
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29 ## Called with a single argument, @code{shiftdim}, removes the leading
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30 ## singleton dimensions, returning the number of dimensions removed
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31 ## in the second output argument @var{ns}.
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32 ##
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33 ## For example:
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34 ##
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35 ## @example
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36 ## @group
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37 ## x = ones (1, 2, 3);
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38 ## size (shiftdim (x, -1))
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39 ## @result{} [1, 1, 2, 3]
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40 ## size (shiftdim (x, 1))
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41 ## @result{} [2, 3]
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42 ## [b, ns] = shiftdim (x)
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43 ## @result{} b = [1, 1, 1; 1, 1, 1]
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44 ## @result{} ns = 1
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45 ## @end group
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46 ## @end example
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47 ## @seealso {reshape, permute, ipermute, circshift, squeeze}
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48 ## @end deftypefn
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49
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50 function [y, ns] = shiftdim (x, n)
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51
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52 if (nargin < 1 || nargin > 2)
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53 print_usage ();
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54 endif
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55
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56 nd = ndims (x);
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57 orig_dims = size (x);
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58
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59 if (nargin == 1)
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60 ## Find the first non-singleton dimension.
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61 (n = find (orig_dims != 1, 1) - 1) || (n = nd);
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62 elseif (! (isscalar (n) && n == fix (n)))
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63 error ("shiftdim: N must be a scalar integer");
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64 endif
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65
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66 if (n >= nd)
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67 n = rem (n, nd);
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68 endif
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69
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70 if (n < 0)
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71 singleton_dims = ones (1, -n);
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72 y = reshape (x, [singleton_dims, orig_dims]);
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73 elseif (n > 0)
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74 ## We need permute here instead of reshape to shift values in a
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75 ## compatible way.
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76 y = permute (x, [n+1:nd 1:n]);
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77 else
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78 y = x;
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79 endif
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80
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81 ns = n;
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82
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83 endfunction
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84
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85
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86 %!test
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87 %! x = rand (1, 1, 4, 2);
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88 %! [y, ns] = shiftdim (x);
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89 %! assert (size (y), [4 2]);
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90 %! assert (ns, 2);
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91 %! assert (shiftdim (y, -2), x);
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92 %! assert (size (shiftdim (x, 2)), [4 2]);
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93
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94 %!assert (size (shiftdim (rand (0, 1, 2))), [0 1 2])
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95
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96 %% Test input validation
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97 %!error (shiftdim ())
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98 %!error (shiftdim (1,2,3))
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99 %!error (shiftdim (1, ones (2)))
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100 %!error (shiftdim (1, 1.5))
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101