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mean.m
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1997-02-19
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## Copyright (C) 1995, 1996, 1997 Kurt Hornik
##
## This program 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 2, or (at your option)
## any later version.
##
## This program 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 this file. If not, write to the Free Software Foundation,
## 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
## usage: mean (x [, opt])
##
## For vector arguments, return the mean the values.
## For matrix arguments, return a row vector containing the mean for
## each column.
##
## With the optional argument opt, the kind of mean computed can be
## selected.
## If opt is "a", the (ordinary) arithmetic mean is computed. This
## is the default.
## If opt is "g", the geometric mean is computed.
## If opt is "h", the harmonic mean is computed.
## Author: KH <Kurt.Hornik@ci.tuwien.ac.at>
## Description: Compute arithmetic, geometric, and harmonic mean
function y = mean (x, opt)
if ((nargin < 1) || (nargin > 2))
usage ("mean (x [, opt])");
endif
if isempty (x)
error ("mean: x must not be empty");
endif
if (rows (x) == 1)
x = x';
endif
if (nargin == 1)
opt = "a";
endif
[r, c] = size (x);
if (strcmp (opt, "a"))
y = sum (x) / r;
elseif (strcmp (opt, "g"))
y = NaN * ones (1, c);
i = find (all (x > 0));
if any (i)
y(i) = exp (sum (log (x(:, i))) / r);
endif
elseif (strcmp (opt, "h"))
y = NaN * ones (1, c);
i = find (all (x != 0));
if any (i)
y(i) = r ./ sum (1 ./ x(:, i));
endif
else
error (sprintf ("mean: option `%s' not recognized", opt));
endif
endfunction