1 ## Copyright (C) 1997-2012 Vincent Cautaerts
3 ## This file is part of Octave.
5 ## Octave is free software; you can redistribute it and/or modify it
6 ## under the terms of the GNU General Public License as published by
7 ## the Free Software Foundation; either version 3 of the License, or (at
8 ## your option) any later version.
10 ## Octave is distributed in the hope that it will be useful, but
11 ## WITHOUT ANY WARRANTY; without even the implied warranty of
12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 ## General Public License for more details.
15 ## You should have received a copy of the GNU General Public License
16 ## along with Octave; see the file COPYING. If not, see
17 ## <http://www.gnu.org/licenses/>.
20 ## @deftypefn {Function File} {} ifftshift (@var{x})
21 ## @deftypefnx {Function File} {} ifftshift (@var{x}, @var{dim})
22 ## Undo the action of the @code{fftshift} function. For even length
23 ## @var{x}, @code{fftshift} is its own inverse, but odd lengths differ
27 ## Author: Vincent Cautaerts <vincent@comf5.comm.eng.osaka-u.ac.jp>
30 ## Modified-By: Paul Kienzle, converted from fftshift
31 ## Modified-By: David Bateman, add NDArray capability and option dim arg
33 function retval = ifftshift (x, dim)
37 if (nargin != 1 && nargin != 2)
43 error ("ifftshift: dimension must be an integer scalar");
47 sz2 = floor (sz(dim) / 2);
48 idx = repmat ({':'}, nd, 1);
49 idx{dim} = [sz2+1:sz(dim), 1:sz2];
55 retval = x([xx+1:xl, 1:xx]);
59 sz2 = floor (sz ./ 2);
62 idx{i} = [sz2(i)+1:sz(i), 1:sz2(i)];
66 error ("ifftshift: expecting vector or matrix argument");
75 %! assert(y, [4 5 6 7 0 1 2 3]);
76 %! assert(ifftshift (y), x);
81 %! assert(y, [3 4 5 6 0 1 2]);
82 %! assert(ifftshift (y), [6 0 1 2 3 4 5]);
87 %! assert(y, [4;5;6;7;0;1;2;3]);
88 %! assert(ifftshift (y), x);
93 %! assert(y, [3;4;5;6;0;1;2]);
94 %! assert(ifftshift (y), [6;0;1;2;3;4;5]);
98 %! x = [x;2*x;3*x+1;4*x+1];
100 %! assert(y, [[7 10 1 4];[9 13 1 5];[2 3 0 1];[4 6 0 2]]);
101 %! assert(ifftshift (y), x);
105 %! x = [x;2*x;3*x+1;4*x+1];
106 %! y = ifftshift (x,1);
107 %! assert(y, [[1 4 7 10];[1 5 9 13];[0 1 2 3];[0 2 4 6]]);
108 %! assert(ifftshift (y,1), x);
112 %! x = [x;2*x;3*x+1;4*x+1];
113 %! y = ifftshift (x,2);
114 %! assert(y, [[2 3 0 1];[4 6 0 2];[7 10 1 4];[9 13 1 5]]);
115 %! assert(ifftshift (y,2), x);