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% DOCBLOCK array_shiftdim
% Copyright (c) 2007 Samit Basu
% Licensed under the GPL
function [y,n] = shiftdim(x,p)
% Compute the size of x
xsize = size(x);
if (nargin == 1)
% Find the first non-singular dimension of x
p = find(xsize ~= 1,1,'first')-1;
end
if (isempty(p) || (p==0))
% Nothing required
y = x;
n = 0;
elseif (p < 0)
% For right shifting (negative p), we just reshape the array
% and introduce extra singleton dimensions
y = reshape(x,[ones(1,-p),xsize]);
n = p;
else
% Left shifting is modulo the number of dimensions of x
p = rem(p,ndims(x));
% For left shifting, (positive p), we can just reshape the
% array, provided that the leading dimensions are all singletons
% We have to make sure that the reshape call has at least two
% dimensions in the shape argument - the number remaining
% is ndims(x)-p
if (all(xsize(1:p)==1))
xsize = xsize((p+1):end);
if (numel(xsize) < 2), xsize = [xsize,1]; end;
y = reshape(x,xsize);
n = p;
else
% a permutation is in order
y = permute(x,[(p+1):ndims(x),1:p]);
n = p;
end
end
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