octave:scripts/statistics/base/mean.m

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scripts/statistics/base/mean.m

changeset 10289:	4b124317dc38
parent:	22a7e4690742
author:	John W. Eaton <jwe@octave.org>
date:	Tue Feb 09 20:58:55 2010 -0500 (70 minutes ago)
permissions:	-rw-r--r--
description:	base_properties::set_children: account for hidden children
     1## Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2002, 2003, 2005,
     2##               2006, 2007, 2008, 2009 Kurt Hornik
     3##
     4## This file is part of Octave.
     5##
     6## Octave is free software; you can redistribute it and/or modify it
     7## under the terms of the GNU General Public License as published by
     8## the Free Software Foundation; either version 3 of the License, or (at
     9## your option) any later version.
    10##
    11## Octave is distributed in the hope that it will be useful, but
    12## WITHOUT ANY WARRANTY; without even the implied warranty of
    13## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    14## General Public License for more details.
    15##
    16## You should have received a copy of the GNU General Public License
    17## along with Octave; see the file COPYING.  If not, see
    18## <http://www.gnu.org/licenses/>.
    19
    20## -*- texinfo -*-
    21## @deftypefn {Function File} {} mean (@var{x}, @var{dim}, @var{opt})
    22## If @var{x} is a vector, compute the mean of the elements of @var{x}
    23## @tex
    24## $$ {\rm mean}(x) = \bar{x} = {1\over N} \sum_{i=1}^N x_i $$
    25## @end tex
    26## @ifnottex
    27##
    28## @example
    29## mean (x) = SUM_i x(i) / N
    30## @end example
    31## @end ifnottex
    32## If @var{x} is a matrix, compute the mean for each column and return them
    33## in a row vector.
    34##
    35## With the optional argument @var{opt}, the kind of mean computed can be
    36## selected.  The following options are recognized:
    37##
    38## @table @code
    39## @item "a"
    40## Compute the (ordinary) arithmetic mean.  This is the default.
    41##
    42## @item "g"
    43## Compute the geometric mean.
    44##
    45## @item "h"
    46## Compute the harmonic mean.
    47## @end table
    48##
    49## If the optional argument @var{dim} is supplied, work along dimension
    50## @var{dim}.
    51##
    52## Both @var{dim} and @var{opt} are optional.  If both are supplied,
    53## either may appear first.
    54## @end deftypefn
    55
    56## Author: KH <Kurt.Hornik@wu-wien.ac.at>
    57## Description: Compute arithmetic, geometric, and harmonic mean
    58
    59function y = mean (x, opt1, opt2)
    60
    61  need_dim = 0;
    62
    63  if (nargin == 1)
    64    opt = "a";
    65    need_dim = 1;
    66  elseif (nargin == 2)
    67    if (ischar (opt1))
    68      opt = opt1;
    69      need_dim = 1;
    70    else
    71      dim = opt1;
    72      opt = "a";
    73    endif
    74  elseif (nargin == 3)
    75    if (ischar (opt1))
    76      opt = opt1;
    77      dim = opt2;
    78    elseif (ischar (opt2))
    79      opt = opt2;
    80      dim = opt1;
    81    else
    82      error ("mean: expecting opt to be a string");
    83    endif
    84  else
    85    print_usage ();
    86  endif
    87
    88  if (need_dim)
    89    t = find (size (x) != 1);
    90    if (isempty (t))
    91      dim = 1;
    92    else
    93      dim = t(1);
    94    endif
    95  endif
    96
    97  if (dim > ndims (x))
    98    n = 1;
    99  else
   100    sz = size (x);
   101    n = sz (dim);
   102  endif
   103
   104  if (strcmp (opt, "a"))
   105    y = sum (x, dim) / n;
   106  elseif (strcmp (opt, "g"))
   107    y = prod (x, dim) .^ (1/n);
   108  elseif (strcmp (opt, "h"))
   109    y = n ./ sum (1 ./ x, dim);
   110  else
   111    error ("mean: option `%s' not recognized", opt);
   112  endif
   113
   114endfunction
   115
   116%!test
   117%! x = -10:10;
   118%! y = x';
   119%! z = [y, y+10];
   120%! assert(mean (x) == 0 && mean (y) == 0 && mean (z) == [0, 10]);
   121
   122%!error mean ();
   123
   124%!error mean (1, 2, 3);
   125