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## Copyright (C) 2004-2013 David Bateman
##
## This file is part of Octave.
##
## Octave is free software; you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 3 of the License, or (at
## your option) any later version.
##
## Octave is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
## General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING. If not, see
## <http://www.gnu.org/licenses/>.
## -*- texinfo -*-
## @deftypefn {Function File} {@var{y} =} circshift (@var{x}, @var{n})
## Circularly shift the values of the array @var{x}. @var{n} must be
## a vector of integers no longer than the number of dimensions in
## @var{x}. The values of @var{n} can be either positive or negative,
## which determines the direction in which the values or @var{x} are
## shifted. If an element of @var{n} is zero, then the corresponding
## dimension of @var{x} will not be shifted. For example:
##
## @example
## @group
## x = [1, 2, 3; 4, 5, 6; 7, 8, 9];
## circshift (x, 1)
## @result{} 7, 8, 9
## 1, 2, 3
## 4, 5, 6
## circshift (x, -2)
## @result{} 7, 8, 9
## 1, 2, 3
## 4, 5, 6
## circshift (x, [0,1])
## @result{} 3, 1, 2
## 6, 4, 5
## 9, 7, 8
## @end group
## @end example
## @seealso {permute, ipermute, shiftdim}
## @end deftypefn
function y = circshift (x, n)
if (nargin != 2)
print_usage ();
endif
if (isempty (x))
y = x;
return;
endif
nd = ndims (x);
sz = size (x);
if (! isvector (n) || length (n) > nd)
error ("circshift: N must be a vector, no longer than the number of dimension in X");
elseif (any (n != fix (n)))
error ("circshift: all values of N must be integers");
endif
idx = repmat ({':'}, 1, nd);
for i = 1:length (n);
b = n(i);
d = sz(i);
if (b > 0)
b = rem (b, d);
idx{i} = [d-b+1:d, 1:d-b];
elseif (b < 0)
b = rem (abs (b), d);
idx{i} = [b+1:d, 1:b];
endif
endfor
y = x(idx{:});
endfunction
%!shared x
%! x = [1, 2, 3; 4, 5, 6; 7, 8, 9];
%!assert (circshift (x, 1), [7, 8, 9; 1, 2, 3; 4, 5, 6])
%!assert (circshift (x, -2), [7, 8, 9; 1, 2, 3; 4, 5, 6])
%!assert (circshift (x, [0, 1]), [3, 1, 2; 6, 4, 5; 9, 7, 8])
%!assert (circshift ([], 1), [])
%!assert (circshift (eye (3), 1), circshift (eye (3), 1))
%!assert (circshift (eye (3), 1), [0,0,1;1,0,0;0,1,0])
%% Test input validation
%!error circshift ()
%!error circshift (1)
%!error circshift (1,2,3)
%!error circshift (1, ones (2,2))
%!error circshift (1, [1 2 3])
%!error circshift (1, 1.5)
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