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1 ## Copyright (C) 1997, 2006, 2007 by Vincent Cautaerts |
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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} {} ifftshift (@var{v}) |
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21 ## @deftypefnx {Function File} {} ifftshift (@var{v}, @var{dim}) |
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22 ## Undo the action of the @code{fftshift} function. For even length |
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23 ## @var{v}, @code{fftshift} is its own inverse, but odd lengths differ |
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24 ## slightly. |
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25 ## @end deftypefn |
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26 |
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27 ## Author: Vincent Cautaerts <vincent@comf5.comm.eng.osaka-u.ac.jp> |
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28 ## Created: July 1997 |
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29 ## Adapted-By: jwe |
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30 ## Modified-By: Paul Kienzle, converted from fftshift |
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31 ## Modified-By: David Bateman, add NDArray capability and option dim arg |
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32 |
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33 function retval = ifftshift (V, dim) |
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34 |
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35 retval = 0; |
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36 |
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37 if (nargin != 1 && nargin != 2) |
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38 print_usage (); |
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39 endif |
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40 |
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41 if (nargin == 2) |
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42 if (!isscalar (dim)) |
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43 error ("ifftshift: dimension must be an integer scalar"); |
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44 endif |
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45 nd = ndims (V); |
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46 sz = size (V); |
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47 sz2 = floor (sz(dim) / 2); |
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48 idx = cell (); |
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49 for i=1:nd |
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50 idx {i} = 1:sz(i); |
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51 endfor |
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52 idx {dim} = [sz2+1:sz(dim), 1:sz2]; |
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53 retval = V (idx{:}); |
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54 else |
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55 if (isvector (V)) |
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56 x = length (V); |
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57 xx = floor (x/2); |
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58 retval = V([xx+1:x, 1:xx]); |
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59 elseif (ismatrix (V)) |
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60 nd = ndims (V); |
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61 sz = size (V); |
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62 sz2 = floor (sz ./ 2); |
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63 idx = cell (); |
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64 for i=1:nd |
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65 idx{i} = [sz2(i)+1:sz(i), 1:sz2(i)]; |
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66 endfor |
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67 retval = V (idx{:}); |
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68 else |
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69 error ("ifftshift: expecting vector or matrix argument"); |
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70 endif |
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71 endif |
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72 |
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73 endfunction |
