time   calls  line
                  1 function y = fftshift(x,dim)
                  2 %FFTSHIFT Shift zero-frequency component to center of spectrum.
                  3 %   For vectors, FFTSHIFT(X) swaps the left and right halves of
                  4 %   X.  For matrices, FFTSHIFT(X) swaps the first and third
                  5 %   quadrants and the second and fourth quadrants.  For N-D
                  6 %   arrays, FFTSHIFT(X) swaps "half-spaces" of X along each
                  7 %   dimension.
                  8 %
                  9 %   FFTSHIFT(X,DIM) applies the FFTSHIFT operation along the 
                 10 %   dimension DIM.
                 11 %
                 12 %   FFTSHIFT is useful for visualizing the Fourier transform with
                 13 %   the zero-frequency component in the middle of the spectrum.
                 14 %
                 15 %   Class support for input X:
                 16 %      float: double, single
                 17 %
                 18 %   See also IFFTSHIFT, FFT, FFT2, FFTN, CIRCSHIFT.
                 19 
                 20 %   Copyright 1984-2004 The MathWorks, Inc.
                 21 %   $Revision: 5.11.4.4 $  $Date: 2010/08/23 23:07:36 $
                 22 
  0.01     866   23 if nargin > 1 
           866   24     if (~isscalar(dim)) || floor(dim) ~= dim || dim < 1 
                 25         error(message('MATLAB:fftshift:DimNotPosInt'))
                 26     end
  0.07     866   27     idx = repmat({':'}, 1, max(ndims(x),dim)); 
           866   28     m = size(x, dim); 
           866   29     p = ceil(m/2); 
  0.07     866   30     idx{dim} = [p+1:m 1:p]; 
                 31 else
                 32     numDims = ndims(x);
                 33     idx = cell(1, numDims);
                 34     for k = 1:numDims
                 35         m = size(x, k);
                 36         p = ceil(m/2);
                 37         idx{k} = [p+1:m 1:p];
                 38     end
                 39 end
                 40 
                 41 % Use comma-separated list syntax for N-D indexing.
  0.14     866   42 y = x(idx{:});