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########################################################################
##
## Copyright (C) 2010-2024 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{A} =} accumdim (@var{subs}, @var{vals})
## @deftypefnx {} {@var{A} =} accumdim (@var{subs}, @var{vals}, @var{dim})
## @deftypefnx {} {@var{A} =} accumdim (@var{subs}, @var{vals}, @var{dim}, @var{n})
## @deftypefnx {} {@var{A} =} accumdim (@var{subs}, @var{vals}, @var{dim}, @var{n}, @var{fcn})
## @deftypefnx {} {@var{A} =} accumdim (@var{subs}, @var{vals}, @var{dim}, @var{n}, @var{fcn}, @var{fillval})
## Create an array by accumulating the slices of an array into the
## positions defined by their subscripts along a specified dimension.
##
## The subscripts are defined by the index vector @var{subs}.
## The dimension is specified by @var{dim}. If not given, it defaults
## to the first non-singleton dimension. The length of @var{subs} must
## be equal to @code{size (@var{vals}, @var{dim})}.
##
## The extent of the result matrix in the working dimension will be
## determined by the subscripts themselves. However, if @var{n} is
## defined it determines this extent.
##
## The default action of @code{accumdim} is to sum the subarrays with the
## same subscripts. This behavior can be modified by defining the
## @var{fcn} function. This should be a function or function handle
## that accepts an array and a dimension, and reduces the array along
## this dimension. As a special exception, the built-in @code{min} and
## @code{max} functions can be used directly, and @code{accumdim}
## accounts for the middle empty argument that is used in their calling.
##
## The slices of the returned array that have no subscripts associated
## with them are set to zero. Defining @var{fillval} to some other
## value allows these values to be defined.
##
## An example of the use of @code{accumdim} is:
##
## @example
## @group
## accumdim ([1, 2, 1, 2, 1], [ 7, -10, 4;
## -5, -12, 8;
## -12, 2, 8;
## -10, 9, -3;
## -5, -3, -13])
## @result{} [-10,-11,-1;-15,-3,5]
## @end group
## @end example
##
## @seealso{accumarray}
## @end deftypefn
function A = accumdim (subs, vals, dim, n = 0, fcn = [], fillval = 0)
if (nargin < 2)
print_usage ();
endif
if (isempty (fillval))
fillval = 0;
endif
if (! isvector (subs))
error ("accumdim: SUBS must be a subscript vector");
elseif (! isindex (subs)) # creates index cache
error ("accumdim: indices must be positive integers");
else
m = max (subs);
if (n == 0 || isempty (n))
n = m;
elseif (n < m)
error ("accumdim: N index out of range");
endif
endif
sz = size (vals);
if (nargin < 3)
## Find the first non-singleton dimension.
(dim = find (sz > 1, 1)) || (dim = 1);
elseif (! isindex (dim))
error ("accumdim: DIM must be a valid dimension");
elseif (dim > length (sz))
sz(end+1:dim) = 1;
endif
sz(dim) = n;
if (length (subs) != size (vals, dim))
error ("accumdim: dimension mismatch");
endif
if (isempty (fcn) || fcn == @sum)
## Fast summation case.
A = __accumdim_sum__ (subs, vals, dim, n);
## Fill in nonzero fill value
if (fillval != 0)
mask = true (n, 1);
mask(subs) = false;
subsc = {':'}(ones (1, length (sz)));
subsc{dim} = mask;
A(subsc{:}) = fillval;
endif
return;
endif
## The general case.
ns = length (subs);
## Sort indices.
[subs, idx] = sort (subs(:));
## Identify runs.
jdx = find (subs(1:ns-1) != subs(2:ns));
jdx = [jdx; ns];
## Collect common slices.
szc = num2cell (sz);
szc{dim} = diff ([0; jdx]);
subsc = {':'}(ones (1, length (sz)));
subsc{dim} = idx;
vals = mat2cell (vals(subsc{:}), szc{:});
## Apply reductions. Special case min, max.
if (fcn == @min || fcn == @max)
vals = cellfun (fcn, vals, {[]}, {dim}, "uniformoutput", false);
else
vals = cellfun (fcn, vals, {dim}, "uniformoutput", false);
endif
subs = subs(jdx);
## Concatenate reduced slices.
vals = cat (dim, vals{:});
## Construct matrix of fillvals.
if (fillval == 0)
A = zeros (sz, class (vals));
else
A = repmat (fillval, sz);
endif
## Set the reduced values.
subsc{dim} = subs;
A(subsc{:}) = vals;
endfunction
## Test accumdim vs. accumarray
%!shared a
%! a = rand (5, 5, 5);
%!assert (accumdim ([1;3;1;3;3], a)(:,2,3), accumarray ([1;3;1;3;3], a(:,2,3)))
%!assert (accumdim ([2;3;2;2;2], a, 2, 4)(4,:,2),
%! accumarray ([2;3;2;2;2], a(4,:,2), [1,4]))
%!assert (accumdim ([2;3;2;1;2], a, 3, 3, @min)(1,5,:),
%! accumarray ([2;3;2;1;2], a(1,5,:), [1,1,3], @min))
%!assert (accumdim ([1;3;2;2;1], a, 2, 3, @median)(4,:,5),
%! accumarray ([1;3;2;2;1], a(4,:,5), [1,3], @median))
## Test fillval
%!assert (accumdim ([1;3;1;3;3], a)(2,:,:), zeros (1,5,5))
%!assert (accumdim ([1;3;1;3;3], a, 1, 4)([2 4],:,:), zeros (2,5,5))
%!assert (accumdim ([1;3;1;3;3], a, 1, 4, [], pi)([2 4],:,:), pi (2,5,5))
## Test input validation
%!error <Invalid call> accumdim ()
%!error <Invalid call> accumdim (1)
%!error <SUBS must be a subscript vector> accumdim (ones (2,2), ones (2,2))
%!error <indices must be positive integers> accumdim ([-1 1], ones (2,2))
%!error <N index out of range> accumdim ([1 2], ones (2,2), 1, 1)
%!error <dimension mismatch> accumdim ([1], ones (2,2))
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