1 ## Copyright (C) 2004-2012 John Eaton and David Bateman
3 ## This file is part of Octave.
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.
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 ## General Public License for more details.
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16 ## along with Octave; see the file COPYING. If not, see
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20 ## @deftypefn {Function File} {@var{y} =} shiftdim (@var{x}, @var{n})
21 ## @deftypefnx {Function File} {[@var{y}, @var{ns}] =} shiftdim (@var{x})
22 ## Shift the dimensions of @var{x} by @var{n}, where @var{n} must be
23 ## an integer scalar. When @var{n} is positive, the dimensions of
24 ## @var{x} are shifted to the left, with the leading dimensions
25 ## circulated to the end. If @var{n} is negative, then the dimensions
26 ## of @var{x} are shifted to the right, with @var{n} leading singleton
29 ## Called with a single argument, @code{shiftdim}, removes the leading
30 ## singleton dimensions, returning the number of dimensions removed
31 ## in the second output argument @var{ns}.
37 ## x = ones (1, 2, 3);
38 ## size (shiftdim (x, -1))
39 ## @result{} [1, 1, 2, 3]
40 ## size (shiftdim (x, 1))
42 ## [b, ns] = shiftdim (x)
43 ## @result{} b = [1, 1, 1; 1, 1, 1]
47 ## @seealso {reshape, permute, ipermute, circshift, squeeze}
50 function [y, ns] = shiftdim (x, n)
52 if (nargin < 1 || nargin > 2)
60 ## Find the first non-singleton dimension.
61 (n = find (orig_dims != 1, 1) - 1) || (n = nd);
62 elseif (! (isscalar (n) && n == fix (n)))
63 error ("shiftdim: N must be a scalar integer");
71 singleton_dims = ones (1, -n);
72 y = reshape (x, [singleton_dims, orig_dims]);
74 ## We need permute here instead of reshape to shift values in a
76 y = permute (x, [n+1:nd 1:n]);
87 %! x = rand (1, 1, 4, 2);
88 %! [y, ns] = shiftdim (x);
89 %! assert (size (y), [4 2]);
91 %! assert (shiftdim (y, -2), x);
92 %! assert (size (shiftdim (x, 2)), [4 2]);
93 %!assert (size (shiftdim (rand (0, 1, 2))), [0 1 2]);
95 %% Test input validation
97 %!error(shiftdim (1,2,3));
98 %!error(shiftdim (1, ones (2)));
99 %!error(shiftdim (1, 1.5));