Mercurial > octave-nkf
view scripts/statistics/base/moment.m @ 5090:c42c90543e36
[project @ 2004-12-03 04:32:11 by jwe]
author | jwe |
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date | Fri, 03 Dec 2004 04:32:11 +0000 |
parents | d62c421f448b |
children | 4c8a2e4e0717 |
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## Copyright (C) 1995, 1996, 1997 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 2, 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, write to the Free ## Software Foundation, 59 Temple Place - Suite 330, Boston, MA ## 02111-1307, USA. ## -*- texinfo -*- ## @deftypefn {Function File} {} moment (@var{x}, @var{p}, @var{opt}, @var{dim}) ## If @var{x} is a vector, compute the @var{p}-th moment of @var{x}. ## ## If @var{x} is a matrix, return the row vector containing the ## @var{p}-th moment of each column. ## ## With the optional string opt, the kind of moment to be computed can ## be specified. If opt contains @code{"c"} or @code{"a"}, central ## and/or absolute moments are returned. For example, ## ## @example ## moment (x, 3, "ac") ## @end example ## ## @noindent ## computes the third central absolute moment of @var{x}. ## ## If the optional argument @var{dim} is supplied, work along dimension ## @var{dim}. ## @end deftypefn ## Can easily be made to work for continuous distributions (using quad) ## as well, but how does the general case work? ## Author: KH <Kurt.Hornik@ci.tuwien.ac.at> ## Description: Compute moments function m = moment (x, p, opt1, opt2) if ((nargin < 2) || (nargin > 4)) usage ("moment (x, p, type, dim)"); endif need_dim = 0; if (nargin == 2) opt = ""; need_dim = 1; elseif (nargin == 3) if (isstr (opt1)) opt = opt1; need_dim = 1; else dim = opt1; opt = ""; endif elseif (nargin == 4) if (isstr (opt1)) opt = opt1; dim = opt2; elseif (isstr (opt2)) opt = opt2; dim = opt1; else usage ("moment: expecting opt to be a string"); endif else usage ("moment (x, p, dim, opt) or moment (x, p, dim, opt)"); endif if (need_dim) t = find (size (x) != 1); if (isempty (t)) dim = 1; else dim = t(1); endif endif sz = size (x); n = sz (dim); if (numel (x) < 1) error ("moment: x must not be empty"); endif tmp = warn_str_to_num; unwind_protect warn_str_to_num = 0; if any (opt == "c") rng = ones(1, length (sz)); rng (dim) = sz (dim); x = x - repmat (sum (x, dim), rng) / n; endif if any (opt == "a") x = abs (x); endif unwind_protect_cleanup warn_str_to_num = tmp; end_unwind_protect m = sum(x .^ p, dim) / n; endfunction