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1 ## Copyright (C) 1997 by Vincent Cautaerts |
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2 ## |
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3 ## This program is free software; you can redistribute it and/or modify |
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4 ## it under the terms of the GNU General Public License as published by |
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5 ## the Free Software Foundation; either version 2, or (at your option) |
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6 ## any later version. |
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7 ## |
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8 ## This program is distributed in the hope that it will be useful, but |
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9 ## WITHOUT ANY WARRANTY; without even the implied warranty of |
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10 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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11 ## General Public License for more details. |
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12 ## |
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13 ## You should have received a copy of the GNU General Public License |
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14 ## along with this file. If not, write to the Free Software Foundation, |
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15 ## 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
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16 |
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17 ## -*- texinfo -*- |
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18 ## @deftypefn {Function File} {} ifftshift (@var{v}) |
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19 ## Undo the action of the fftshift function. For even length @var{v}, fftshift |
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20 ## is its own inverse, but odd lengths differ slightly. |
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21 ## @end deftypefn |
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22 |
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23 ## Author: Vincent Cautaerts <vincent@comf5.comm.eng.osaka-u.ac.jp> |
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24 ## Created: July 1997 |
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25 ## Adapted-By: jwe |
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26 ## Modified-By: Paul Kienzle, converted from fftshift |
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27 |
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28 function retval = ifftshift (V) |
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29 |
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30 retval = 0; |
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31 |
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32 if (nargin != 1) |
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33 usage ("usage: ifftshift (X)"); |
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34 endif |
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35 |
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36 if (is_vector (V)) |
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37 x = length (V); |
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38 xx = floor (x/2); |
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39 retval = V([xx+1:x, 1:xx]); |
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40 elseif (is_matrix (V)) |
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41 [x, y] = size (V); |
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42 xx = floor (x/2); |
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43 yy = floor (y/2); |
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44 retval = V([xx+1:x, 1:xx], [yy+1:y, 1:yy]); |
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45 else |
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46 error ("ifftshift: expecting vector or matrix argument"); |
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47 endif |
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48 |
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49 endfunction |
