Mercurial > octave
view scripts/statistics/base/center.m @ 23219:3ac9f9ecfae5 stable
maint: Update copyright dates.
author | John W. Eaton <jwe@octave.org> |
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date | Wed, 22 Feb 2017 12:39:29 -0500 |
parents | e9a0469dedd9 |
children | 092078913d54 |
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## Copyright (C) 1995-2017 Kurt Hornik ## Copyright (C) 2009 VZLU Prague ## ## 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 {} {} center (@var{x}) ## @deftypefnx {} {} center (@var{x}, @var{dim}) ## Center data by subtracting its mean. ## ## If @var{x} is a vector, subtract its mean. ## ## If @var{x} is a matrix, do the above for each column. ## ## If the optional argument @var{dim} is given, operate along this dimension. ## ## Programming Note: @code{center} has obvious application for normalizing ## statistical data. It is also useful for improving the precision of general ## numerical calculations. Whenever there is a large value that is common ## to a batch of data, the mean can be subtracted off, the calculation ## performed, and then the mean added back to obtain the final answer. ## @seealso{zscore} ## @end deftypefn ## Author: KH <Kurt.Hornik@wu-wien.ac.at> ## Description: Center by subtracting means function retval = center (x, dim) if (nargin != 1 && nargin != 2) print_usage (); endif if (! (isnumeric (x) || islogical (x))) error ("center: X must be a numeric vector or matrix"); endif if (isinteger (x)) x = double (x); endif nd = ndims (x); sz = size (x); if (nargin != 2) ## Find the first non-singleton dimension. (dim = find (sz > 1, 1)) || (dim = 1); else if (! (isscalar (dim) && dim == fix (dim) && dim > 0)) error ("center: DIM must be an integer and a valid dimension"); endif endif n = size (x, dim); if (n == 0) retval = x; else retval = x - mean (x, dim); endif endfunction %!assert (center ([1,2,3]), [-1,0,1]) %!assert (center (single ([1,2,3])), single ([-1,0,1])) %!assert (center (int8 ([1,2,3])), [-1,0,1]) %!assert (center (logical ([1, 0, 0, 1])), [0.5, -0.5, -0.5, 0.5]) %!assert (center (ones (3,2,0,2)), zeros (3,2,0,2)) %!assert (center (ones (3,2,0,2, "single")), zeros (3,2,0,2, "single")) %!assert (center (magic (3)), [3,-4,1;-2,0,2;-1,4,-3]) %!assert (center ([1 2 3; 6 5 4], 2), [-1 0 1; 1 0 -1]) %!assert (center (1, 3), 0) ## Test input validation %!error center () %!error center (1, 2, 3) %!error <DIM must be an integer> center (1, ones (2,2)) %!error <DIM must be an integer> center (1, 1.5) %!error <DIM must be .* a valid dimension> center (1, 0)