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annotate scripts/signal/ifftshift.m @ 12676:2783fa95cab7

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Use common code idiom for creating cell array for indexing ND-arrays * int2str.m, interpft.m, num2str.m, postpad.m, prepad.m, shift.m, fftshift.m, ifftshift.m, unwrap.m
author Rik <octave@nomad.inbox5.com>
date Sun, 15 May 2011 10:50:30 -0700
parents dd2c70b30f28
children 72c96de7a403
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1 ## Copyright (C) 1997-2011 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{x})
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21 ## @deftypefnx {Function File} {} ifftshift (@var{x}, @var{dim})
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22 ## Undo the action of the @code{fftshift} function. For even length
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23 ## @var{x}, @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 (x, 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 (x);
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46 sz = size (x);
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47 sz2 = floor (sz(dim) / 2);
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48 idx = repmat ({':'}, nd, 1);
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49 idx{dim} = [sz2+1:sz(dim), 1:sz2];
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50 retval = x(idx{:});
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51 else
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52 if (isvector (x))
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53 xl = length (x);
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54 xx = floor (xl/2);
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55 retval = x([xx+1:xl, 1:xx]);
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56 elseif (ismatrix (x))
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57 nd = ndims (x);
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58 sz = size (x);
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59 sz2 = floor (sz ./ 2);
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60 idx = cell ();
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61 for i = 1:nd
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62 idx{i} = [sz2(i)+1:sz(i), 1:sz2(i)];
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63 endfor
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64 retval = x(idx{:});
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65 else
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66 error ("ifftshift: expecting vector or matrix argument");
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67 endif
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68 endif
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69
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70 endfunction
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71
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72 %!test
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73 %! x = [0:7];
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74 %! y = ifftshift (x);
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75 %! assert(y, [4 5 6 7 0 1 2 3]);
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76 %! assert(ifftshift (y), x);
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77
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78 %!test
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79 %! x = [0:6];
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80 %! y = ifftshift (x);
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81 %! assert(y, [3 4 5 6 0 1 2]);
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82 %! assert(ifftshift (y), [6 0 1 2 3 4 5]);
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83
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84 %!test
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85 %! x = [0:7]';
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86 %! y = ifftshift (x);
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87 %! assert(y, [4;5;6;7;0;1;2;3]);
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88 %! assert(ifftshift (y), x);
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89
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90 %!test
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91 %! x = [0:6]';
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92 %! y = ifftshift (x);
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93 %! assert(y, [3;4;5;6;0;1;2]);
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94 %! assert(ifftshift (y), [6;0;1;2;3;4;5]);
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95
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96 %!test
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97 %! x = [0:3];
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98 %! x = [x;2*x;3*x+1;4*x+1];
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99 %! y = ifftshift (x);
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100 %! assert(y, [[7 10 1 4];[9 13 1 5];[2 3 0 1];[4 6 0 2]]);
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101 %! assert(ifftshift (y), x);
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102
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103 %!test
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104 %! x = [0:3];
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105 %! x = [x;2*x;3*x+1;4*x+1];
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106 %! y = ifftshift (x,1);
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107 %! assert(y, [[1 4 7 10];[1 5 9 13];[0 1 2 3];[0 2 4 6]]);
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108 %! assert(ifftshift (y,1), x);
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109
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110 %!test
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111 %! x = [0:3];
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112 %! x = [x;2*x;3*x+1;4*x+1];
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113 %! y = ifftshift (x,2);
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114 %! assert(y, [[2 3 0 1];[4 6 0 2];[7 10 1 4];[9 13 1 5]]);
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115 %! assert(ifftshift (y,2), x);
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116