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view extra/ver20/nanmedian.m @ 0:6b33357c7561 octave-forge
Initial revision
author | pkienzle |
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date | Wed, 10 Oct 2001 19:54:49 +0000 |
parents | |
children | 143f3827b789 |
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## Copyright (C) 2001 Paul Kienzle ## ## 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 ## v = nanmedian(X [, dim]); ## nanmedian is identical to the median function except that NaN values are ## ignored. If all values are NaN, the median is returned as NaN. ## [Is this behaviour compatible?] ## ## See also: nanmin, nanmax, nansum, nanmean function v = nanmedian (X, dim) if nargin < 1 || nargin > 2 usage ("v = nanmean(X [, dim])"); else if nargin == 1 if size(X,1) == 1 dim = 2; else dim = 1; endif endif if (dim == 2) X = X.'; endif dfi = do_fortran_indexing; pzoi = prefer_zero_one_indexing; unwind_protect do_fortran_indexing = 1; prefer_zero_one_indexing = 1; ## Find lengths of datasets after excluding NaNs; valid datasets ## are those that are not empty after you remove all the NaNs n = size(X,1) - sum (isnan(X)); valid = find(n!=0); ## Extract all non-empty datasets and sort, replacing NaN with Inf ## so that the invalid elements go toward the ends of the columns X (isnan(X)) = Inf; X = sort ( X (:, valid) ); ## Determine the offset for each remaining column in single index mode colidx = (0:size(X,2)-1)*size(X,1); ## Assume the median for all datasets will be NaNs v = NaN*ones(size(n)); ## Average the two central values of the sorted list to compute ## the median, but only do so for valid rows. If the dataset ## is odd length, the single central value will be used twice. ## E.g., ## for n==5, ceil(2.5+0.4) is 3 and floor(2.5+0.6) is also 3 ## for n==6, ceil(3.0+0.4) is 4 and floor(3.0+0.6) is 3 v(valid) = ( X (colidx + floor(n(valid)./2+0.6)) ... + X (colidx + ceil(n(valid)./2+0.4)) ) ./ 2; unwind_protect_cleanup do_fortran_indexing = dfi; prefer_zero_one_indexing = pzoi; end_unwind_protect if (dim == 2) v = v.'; endif endif endfunction