X-Git-Url: https://git.creatis.insa-lyon.fr/pubgit/?p=CreaPhase.git;a=blobdiff_plain;f=octave_packages%2Fstatistics-1.1.3%2Fnanvar.m;fp=octave_packages%2Fstatistics-1.1.3%2Fnanvar.m;h=e8e15aa543d15601ee1c7b014146445c6e593ad0;hp=0000000000000000000000000000000000000000;hb=c880e8788dfc484bf23ce13fa2787f2c6bca4863;hpb=1705066eceaaea976f010f669ce8e972f3734b05

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+# Copyright (C) 2008 Sylvain Pelissier <sylvain.pelissier@gmail.com>
+##
+## 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 3 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, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {} nanvar (@var{x})
+## @deftypefnx{Function File} {@var{v} =} nanvar (@var{X}, @var{opt})
+## @deftypefnx{Function File} {@var{v} =} nanvar (@var{X}, @var{opt}, @var{dim})
+## Compute the variance while ignoring NaN values.
+##
+## For vector arguments, return the (real) variance of the values.
+## For matrix arguments, return a row vector containing the variance for
+## each column.
+##
+## The argument @var{opt} determines the type of normalization to use.
+## Valid values are
+##
+## @table @asis 
+## @item 0:
+## Normalizes with @math{N-1}, provides the best unbiased estimator of the
+## variance [default].
+## @item 1:
+## Normalizes with @math{N}, this provides the second moment around the mean.
+## @end table
+##
+## The third argument @var{dim} determines the dimension along which the 
+## variance is calculated.
+##
+## @seealso{var, nanmean, nanstd, nanmax, nanmin}
+## @end deftypefn
+
+function y = nanvar(x,w,dim)
+  if nargin < 1
+    print_usage ();
+  else
+    if ((nargin < 2) || isempty(w))
+      w = 0;
+    endif
+    
+    if nargin < 3
+      dim = min(find(size(x)>1));
+      if isempty(dim)
+        dim=1;
+      endif
+    endif
+    
+    y = nanstd(x,w,dim).^2;
+  endif
+endfunction
+
+## Tests
+%!shared x
+%! x = [1 2 nan 3 4 5];
+%!assert (nanvar (x), var (x(! isnan (x))), 10*eps)