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1 ## Copyright (C) 2004 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}} = circshift (@var{x}, @var{n}) |
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22 ## Circularly shifts the values of the array @var{x}. @var{n} must be |
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23 ## a vector of integers no longer than the number of dimensions in |
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24 ## @var{x}. The values of @var{n} can be either positive or negative, |
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25 ## which determines the direction in which the values or @var{x} are |
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26 ## shifted. If an element of @var{n} is zero, then the corresponding |
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27 ## dimension of @var{x} will not be shifted. For example |
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28 ## |
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29 ## @example |
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30 ## @group |
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31 ## x = [1, 2, 3; 4, 5, 6, 7, 8, 9]; |
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32 ## circshift (x, 1) |
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33 ## @result{} 7, 8, 9 |
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34 ## 1, 2, 3 |
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35 ## 4, 5, 6 |
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36 ## circshift (x, -2) |
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37 ## @result{} 7, 8, 9 |
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38 ## 1, 2, 3 |
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39 ## 4, 5, 6 |
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40 ## circshift (x, [0,1]) |
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41 ## @result{} 3, 1, 2 |
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42 ## 6, 4, 5 |
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43 ## 9, 7, 8 |
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44 ## @end group |
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45 ## @end example |
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46 ## @end deftypefn |
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47 ## |
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48 ## @seealso {permute, ipermute, shiftdim} |
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49 |
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50 function y = circshift (x, n) |
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51 |
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52 if (nargin == 2) |
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53 nd = ndims (x); |
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54 sz = size (x); |
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55 |
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56 if (! isvector (n) && length (n) > nd) |
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57 error ("circshift: n must be a vector, no longer than the number of dimension in x"); |
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58 endif |
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59 |
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60 if (any (n != floor (n))) |
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61 error ("circshift: all values of n must be integers"); |
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62 endif |
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63 |
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64 idx = cell (); |
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65 for i = 1:length (n); |
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66 nn = n(i); |
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67 if (nn < 0) |
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68 while (sz(i) <= -nn) |
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69 nn = nn + sz(i); |
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70 endwhile |
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71 idx{i} = [(1-nn):sz(i), 1:-nn]; |
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72 else |
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73 while (sz(i) <= nn) |
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74 nn = nn - sz(i); |
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75 endwhile |
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76 idx{i} = [(sz(i)-nn+1):sz(i), 1:(sz(i)-nn)]; |
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77 endif |
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78 endfor |
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79 for i = (length(n) + 1) : nd |
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80 idx{i} = 1:sz(i); |
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81 endfor |
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82 y = x(idx{:}); |
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83 else |
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84 usage ("circshift (x, n)"); |
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85 endif |
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86 endfunction |
