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## Copyright (C) 1995-2013 Kurt Hornik
##
## 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{z}, @var{mu}, @var{sigma}] =} zscore (@var{x})
## @deftypefnx {Function File} {[@var{z}, @var{mu}, @var{sigma}] =} zscore (@var{x}, @var{opt})
## @deftypefnx {Function File} {[@var{z}, @var{mu}, @var{sigma}] =} zscore (@var{x}, @var{opt}, @var{dim})
## If @var{x} is a vector, subtract its mean and divide by its standard
## deviation. If the standard deviation is zero, divide by 1 instead.
## The optional parameter @var{opt} determines the normalization to use
## when computing the standard deviation and is the same as the
## corresponding parameter for @code{std}.
##
## If @var{x} is a matrix, do the above along the first non-singleton
## dimension. If the third optional argument @var{dim} is given, operate
## along this dimension.
##
## The mean and standard deviation along @var{dim} are given in @var{mu}
## and @var{sigma} respectively.
##
## @seealso{mean, std, center}
## @end deftypefn
## Author: KH <Kurt.Hornik@wu-wien.ac.at>
## Description: Subtract mean and divide by standard deviation
function [z, mu, sigma] = zscore (x, opt, dim)
if (nargin < 1 || nargin > 3 )
print_usage ();
endif
if (! (isnumeric (x) || islogical (x)))
error ("zscore: X must be a numeric vector or matrix");
endif
if (nargin < 2)
opt = 0;
else
if (opt != 0 && opt != 1 || ! isscalar (opt))
error ("zscore: OPT must be empty, 0, or 1");
endif
endif
nd = ndims (x);
sz = size (x);
if (nargin < 3)
## Find the first non-singleton dimension.
(dim = find (sz > 1, 1)) || (dim = 1);
else
if (!(isscalar (dim) && dim == fix (dim))
|| !(1 <= dim && dim <= nd))
error ("zscore: DIM must be an integer and a valid dimension");
endif
endif
n = sz(dim);
if (n == 0)
z = x;
else
if (isinteger (x))
x = double (x);
endif
mu = mean (x, dim);
sigma = std (x, opt, dim);
s = sigma;
s(s==0) = 1;
## FIXME: Use normal broadcasting once we can disable that warning
z = bsxfun (@rdivide, bsxfun (@minus, x, mu), s);
endif
endfunction
%!assert (zscore ([1,2,3]), [-1,0,1])
%!assert (zscore (single ([1,2,3])), single ([-1,0,1]))
%!assert (zscore (int8 ([1,2,3])), [-1,0,1])
%!assert (zscore (ones (3,2,2,2)), zeros (3,2,2,2))
%!assert (zscore ([2,0,-2;0,2,0;-2,-2,2]), [1,0,-1;0,1,0;-1,-1,1])
%% Test input validation
%!error zscore ()
%!error zscore (1, 2, 3)
%!error zscore (['A'; 'B'])
%!error zscore (1, ones (2,2))
%!error zscore (1, 1.5)
%!error zscore (1, 1, 0)
%!error zscore (1, 3)
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