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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 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 ## Shifts the dimension 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 singleton dimension. |
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61 n = 0; |
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62 while (n < nd && orig_dims(n+1) == 1) |
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63 n++; |
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64 endwhile |
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65 endif |
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66 |
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67 if (! isscalar (n) || floor (n) != n) |
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68 error ("shiftdim: n must be a scalar integer"); |
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69 endif |
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70 |
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71 if (n >= nd) |
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72 n = rem (n, nd); |
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73 endif |
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74 |
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75 if (n < 0) |
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76 singleton_dims = ones (1, -n); |
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77 y = reshape (x, [singleton_dims, orig_dims]); |
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78 elseif (n > 0) |
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79 ## We need permute here instead of reshape to shift values in a |
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80 ## compatible way. |
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81 y = permute (x, [n+1:ndims(x) 1:n]); |
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82 else |
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83 y = x; |
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84 endif |
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85 |
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86 ns = n; |
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87 |
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88 endfunction |
