view scripts/statistics/center.m @ 30997:5330efaf9476

Add optional second output to var and std (bug #62395) * scripts/statistics/var.m: Add optional second output containing the mean used to calculate the variance. Move weight isempty check ahead of vector dimension isscalar check to avoid triggering incompatability error. Add BISTs testing second output with different calling options. Add BIST testing empty value passed as variance weight treated as zero. Add new output behavior to docstring, and update function definitions to show the primary variable. * scripts/statistics/std.m: Add passthrough for second output from var when std called with two outputs. Add BISTs testing second output with different calling options. Update docstring noting new output behavior. * etc/NEWS.8.md: Note output changes to var and std under Matlab Compatability.
author Nicholas R. Jankowski <jankowski.nicholas@gmail.com>
date Thu, 12 May 2022 13:10:52 -0400
parents 5d3faba0342e
children 597f3ee61a48
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########################################################################
##
## Copyright (C) 1995-2022 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} =} center (@var{x})
## @deftypefnx {} {@var{y} =} 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

function y = center (x, dim)

  if (nargin < 1)
    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)
    y = x;
  else
    ## FIXME: Use bsxfun, rather than broadcasting, until broadcasting
    ##        supports diagonal and sparse matrices (Bugs #41441, #35787).
    y = bsxfun (@minus, x, mean (x, dim));
    ## y = x - mean (x, dim);   # automatic broadcasting
  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 <Invalid call> center ()
%!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)