update packages

[CreaPhase.git] / octave_packages / m / statistics / base / mean.m

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+## Copyright (C) 1995-2012 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} {} mean (@var{x})
+## @deftypefnx {Function File} {} mean (@var{x}, @var{dim})
+## @deftypefnx {Function File} {} mean (@var{x}, @var{opt})
+## @deftypefnx {Function File} {} mean (@var{x}, @var{dim}, @var{opt})
+## Compute the mean of the elements of the vector @var{x}.
+## @tex
+## $$ {\rm mean}(x) = \bar{x} = {1\over N} \sum_{i=1}^N x_i $$
+## @end tex
+## @ifnottex
+##
+## @example
+## mean (x) = SUM_i x(i) / N
+## @end example
+##
+## @end ifnottex
+## If @var{x} is a matrix, compute the mean for each column and return them
+## in a row vector.
+##
+## The optional argument @var{opt} selects the type of mean to compute.
+## The following options are recognized:
+##
+## @table @asis
+## @item "a"
+## Compute the (ordinary) arithmetic mean.  [default]
+##
+## @item "g"
+## Compute the geometric mean.
+##
+## @item "h"
+## Compute the harmonic mean.
+## @end table
+##
+## If the optional argument @var{dim} is given, operate along this dimension.
+##
+## Both @var{dim} and @var{opt} are optional.  If both are supplied,
+## either may appear first.
+## @seealso{median, mode}
+## @end deftypefn
+
+## Author: KH <Kurt.Hornik@wu-wien.ac.at>
+## Description: Compute arithmetic, geometric, and harmonic mean
+
+function y = mean (x, opt1, opt2)
+
+  if (nargin < 1 || nargin > 3)
+    print_usage ();
+  endif
+
+  if (! (isnumeric (x) || islogical (x)))
+    error ("mean: X must be a numeric vector or matrix");
+  endif
+
+  need_dim = false;
+
+  if (nargin == 1)
+    opt = "a";
+    need_dim = true;
+  elseif (nargin == 2)
+    if (ischar (opt1))
+      opt = opt1;
+      need_dim = true;
+    else
+      dim = opt1;
+      opt = "a";
+    endif
+  elseif (nargin == 3)
+    if (ischar (opt1))
+      opt = opt1;
+      dim = opt2;
+    elseif (ischar (opt2))
+      opt = opt2;
+      dim = opt1;
+    else
+      error ("mean: OPT must be a string");
+    endif
+  else
+    print_usage ();
+  endif
+
+  nd = ndims (x);
+  sz = size (x);
+  if (need_dim)
+    ## 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 ("mean: DIM must be an integer and a valid dimension");
+    endif
+  endif
+
+  n = sz(dim);
+
+  if (strcmp (opt, "a"))
+    y = sum (x, dim) / n;
+  elseif (strcmp (opt, "g"))
+    y = prod (x, dim) .^ (1/n);
+  elseif (strcmp (opt, "h"))
+    y = n ./ sum (1 ./ x, dim);
+  else
+    error ("mean: option `%s' not recognized", opt);
+  endif
+
+endfunction
+
+
+%!test
+%! x = -10:10;
+%! y = x';
+%! z = [y, y+10];
+%! assert(mean (x) == 0);
+%! assert(mean (y) == 0);
+%! assert(mean (z) == [0, 10]);
+
+%!assert(mean (magic(3), 1), [5, 5, 5]);
+%!assert(mean (magic(3), 2), [5; 5; 5]);
+%!assert(mean ([2 8], 'g'), 4);
+%!assert(mean ([4 4 2], 'h'), 3);
+%!assert(mean (logical ([1 0 1 1])), 0.75);
+%!assert(mean (single ([1 0 1 1])), single (0.75));
+
+%% Test input validation
+%!error mean ();
+%!error mean (1, 2, 3, 4);
+%!error mean ({1:5});
+%!error mean (1, 2, 3);
+%!error mean (1, ones(2,2));
+%!error mean (1, 1.5);
+%!error mean (1, 0);
+%!error mean (1, 3);
+%!error mean (1, 'b');
+