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########################################################################
##
## Copyright (C) 2004-2024 The Octave Project Developers
##
## See the file COPYRIGHT.md in the top-level directory of this
## distribution or <https://octave.org/copyright/>.
##
## 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
## <https://www.gnu.org/licenses/>.
##
########################################################################
## -*- texinfo -*-
## @deftypefn {} {@var{y} =} circshift (@var{x}, @var{n})
## @deftypefnx {} {@var{y} =} circshift (@var{x}, @var{n}, @var{dim})
## 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 of @var{x} are shifted. If an
## element of @var{n} is zero, then the corresponding dimension of @var{x} will
## not be shifted. If @var{n} is a scalar and no @var{dim} is specified then
## the shift is applied to the first non-singular dimension.
##
## If a scalar @var{dim} is given then operate along the specified dimension.
## In this case @var{n} must be a scalar as well.
##
## Examples:
##
## @example
## x = [1, 2, 3;
## 4, 5, 6;
## 7, 8, 9];
## ## positive shift on rows (1st non-singular dim)
## circshift (x, 1)
## @result{}
## 7 8 9
## 1 2 3
## 4 5 6
## ## negative shift on rows (1st non-singular dim)
## circshift (x, -2)
## @result{}
## 7 8 9
## 1 2 3
## 4 5 6
## ## no shift of rows, shift columns by 1 (2nd dimension)
## circshift (x, [0,1])
## @result{}
## 3 1 2
## 6 4 5
## 9 7 8
## ## shift columns (2nd dimension)
## circshift (x, 1, 2)
## @result{}
## 3 1 2
## 6 4 5
## 9 7 8
## @end example
## @seealso{permute, ipermute, shiftdim}
## @end deftypefn
function y = circshift (x, n, dim)
if (nargin < 2)
print_usage ();
endif
if (isempty (x))
y = x;
return;
endif
nd = ndims (x);
sz = size (x);
if (nargin == 2)
if (isscalar (n))
## Find the first non-singleton dimension.
(dim = find (sz > 1, 1)) || (dim = 1);
n = [zeros(1, dim-1), n];
endif
elseif (nargin == 3)
if ( ! isscalar (n))
error ("circshift: N must be a scalar when DIM is also specified");
endif
n = [zeros(1, dim-1), n];
endif
if (! isvector (n) || length (n) > nd)
error ("circshift: N must be a vector, no longer than the number of dimensions 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])
%!assert (circshift (x, -2, 1), [7, 8, 9; 1, 2, 3; 4, 5, 6])
%!assert (circshift (x, 1, 2), [3, 1, 2; 6, 4, 5; 9, 7, 8])
%!test <*53178> assert (circshift (1:4, 1), [4 1 2 3])
%!test <*53178> assert (circshift (1:4, 1, 1), 1:4)
## Test input validation
%!error <Invalid call> circshift ()
%!error <Invalid call> circshift (1)
%!error <N must be a scalar> circshift (1, [2 3], 4)
%!error <N must be a vector> circshift (1, ones (2,2))
%!error <no longer than the number of dimensions in X> circshift (1, [1 2 3])
%!error <all values of N must be integers> circshift (1, 1.5)
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