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[CreaPhase.git] / octave_packages / m / general / circshift.m

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+## Copyright (C) 2004-2012 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)
+