## Copyright (C) 1995-2011 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} {} statistics (@var{x})
## @deftypefnx {Function File} {} statistics (@var{x}, @var{dim})
## Return a vector with the minimum, first quartile, median, third quartile,
## maximum, mean, standard deviation, skewness, and kurtosis of the elements of
## the vector @var{x}.
##
## If @var{x} is a matrix, calculate statistics over the first 
## non-singleton dimension.
## If the optional argument @var{dim} is given, operate along this dimension.
## @seealso{min,max,median,mean,std,skewness,kurtosis}
## @end deftypefn

## Author: KH <Kurt.Hornik@wu-wien.ac.at>
## Description: Compute basic statistics

function stats = statistics (x, dim)

  if (nargin != 1 && nargin != 2)
    print_usage ();
  endif

  if (!isnumeric(x))
    error ("statistics: X must be a numeric vector or matrix");
  endif

  nd = ndims (x);
  sz = size (x);
  if (nargin != 2)
    ## Find the first non-singleton dimension.
    dim = find (sz > 1, 1);
    if (isempty (dim))
      dim = 1;
    endif
  else
    if (!(isscalar (dim) && dim == round (dim))
        || !(1 <= dim && dim <= nd))
      error ("statistics: DIM must be an integer and a valid dimension");
    endif
  endif
  
  if (sz(dim) < 2)
    error ("statistics: dimension of X is too small (<2)");
  endif    

  emp_inv = quantile (x, [0.25; 0.5; 0.75], dim, 7);

  stats = cat (dim, min (x, [], dim), emp_inv, max (x, [], dim), mean (x, dim),
               std (x, [], dim), skewness (x, dim), kurtosis (x, dim));

endfunction

%!test
%! x = rand(7,5);
%! s = statistics (x);
%! m = median (x);
%! assert (m, s(3,:), eps);

%% Test input validation
%!error statistics ()
%!error statistics (1, 2, 3)
%!error statistics ([true true])
%!error statistics (1, ones(2,2))
%!error statistics (1, 1.5)
%!error statistics (1, 0)
%!error statistics (1, 3)
%!error statistics (1)