zeromean

 function f = zeromean(m,dim)

 <m> is a matrix
 <dim> (optional) is the dimension of interest.
   if supplied, subtract off the mean of each case oriented along <dim>.
   if [] or not supplied, subtract off the global mean.

 subtract off the mean of <m>, either of individual cases or the global mean.
 we use nanmean to deal with NaNs gracefully.

 note some weird cases:
   zeromean([]) is []
   zeromean([NaN NaN]) is [NaN NaN]

 example:
 a = [1 1; 2 0];
 isequal(zeromean(a),[0 0; 1 -1])
 a = [1 NaN];
 isequalwithequalnans(zeromean(a,1),[0 NaN])

0001 function f = zeromean(m,dim)
0002 
0003 % function f = zeromean(m,dim)
0004 %
0005 % <m> is a matrix
0006 % <dim> (optional) is the dimension of interest.
0007 %   if supplied, subtract off the mean of each case oriented along <dim>.
0008 %   if [] or not supplied, subtract off the global mean.
0009 %
0010 % subtract off the mean of <m>, either of individual cases or the global mean.
0011 % we use nanmean to deal with NaNs gracefully.
0012 %
0013 % note some weird cases:
0014 %   zeromean([]) is []
0015 %   zeromean([NaN NaN]) is [NaN NaN]
0016 %
0017 % example:
0018 % a = [1 1; 2 0];
0019 % isequal(zeromean(a),[0 0; 1 -1])
0020 % a = [1 NaN];
0021 % isequalwithequalnans(zeromean(a,1),[0 NaN])
0022 
0023 % do it
0024 if ~exist('dim','var') || isempty(dim)
0025   f = m - nanmean(m(:));
0026 else
0027   f = bsxfun(@minus,m,nanmean(m,dim));
0028 end