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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, 59 Temple Place - Suite 330, Boston, MA |
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18 ## 02111-1307, 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 negative, 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 positive, then the dimensions |
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27 ## of @var{x} are shifted to the right, with the @var{n} 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{} [2, 3, 1] |
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41 ## size (shiftdim (x, 1)) |
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42 ## @result{} [1, 1, 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 ## @end deftypefn |
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49 ## @seealso {reshape, permute, ipermute, circshift, squeeze} |
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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) |
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54 ## Find the first singleton dimension. |
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55 nd = ndims (x); |
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56 orig_dims = size (x); |
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57 ns = 1; |
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58 while (ns < nd + 1 && orig_dims(ns) == 1) |
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59 ns = ns + 1; |
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60 endwhile |
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61 if (ns > nd) |
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62 ns = 1; |
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63 endif |
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64 y = reshape (x, orig_dims(ns:end)); |
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65 ns = ns - 1; |
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66 elseif (nargin == 2) |
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67 if (! isscalar (n) && floor (n) != n) |
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68 error ("shiftdim: n must be an scalar integer"); |
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69 endif |
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70 if (n < 0) |
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71 orig_dims = size (x); |
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72 singleton_dims = ones (1, -n); |
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73 y = reshape (x, [singleton_dims, orig_dims]); |
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74 elseif (n > 0) |
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75 ndims = length (size (x)); |
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76 y = permute (x, [n+1:ndims, 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 else |
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81 usage ("shiftdim (x, n) or [b, ns] = shiftdim (x)"); |
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82 endif |
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83 endfunction |
