var.m

来自「matlab数字信号处理工具箱」· M 代码 · 共 62 行

function y=var(x,opt,DIM)
% VAR calculates the variance.
% 
% y = var(x [, opt[, DIM]])
%   calculates the variance in dimension DIM
%   the default DIM is the first non-single dimension
%
% opt   option (not supported)
% DIM	dimension
%	1: VAR of columns
%	2: VAR of rows
% 	N: VAR of  N-th dimension 
%	default or []: first DIMENSION, with more than 1 element
%
% features:
% - can deal with NaN's (missing values)
% - dimension argument 
% - compatible to Matlab and Octave
%
% see also: MEANSQ, SUMSQ, SUMSKIPNAN, MEAN, RMS, STD,

%    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 of the License, 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 program; if not, write to the Free Software
%    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

%	$Revision: 1.17 $
%	$Id: var.m,v 1.17 2003/10/27 17:21:36 schloegl Exp $
%	Copyright (C) 2000-2003 by  Alois Schloegl  <[e-mail]>	

if nargin>1,
        if ~isempty(opt) & opt~=0, 
                fprintf(2,'Warning STD: OPTION not supported.\n');
        end;
else 
        opt = 0; 
end;

if nargin > 2,
        [s,n,y] = sumskipnan(x, DIM);
else
	[s,n,y] = sumskipnan(x);
end

% actual calculation 
y = (y - (real(s).^2+imag(s).^2)./n);   % n * (summed squares with removed mean)

%if flag_implicit_unbiased_estim;    %% ------- unbiased estimates ----------- 
    n = max(n-1,0);			% in case of n=0 and n=1, the (biased) variance, STD and STE are INF
%end;
y = y./n;	% normalize