www.pudn.com > voicebox2.zip > LOGSUM.M

function y=logsum(x,d) 
%LOGSUM logsum(x,d)=log(sum(exp(x),d)) 
%  d gives dimension to sum along 
 
%      Copyright (C) Mike Brookes 1998 
% 
%      Last modified Mon Oct 12 15:47:25 1998 
% 
%   VOICEBOX is a MATLAB toolbox for speech processing. Home page is at 
%   http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html 
% 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
%   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 can obtain a copy of the GNU General Public License from 
%   ftp://prep.ai.mit.edu/pub/gnu/COPYING-2.0 or by writing to 
%   Free Software Foundation, Inc.,675 Mass Ave, Cambridge, MA 02139, USA. 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
 
if nargin==1 
   d=[find(size(x)-1) 1]; 
   d=d(1); 
end 
n=size(x,d); 
if n<=1, y=x; return; end 
s=size(x); 
p=[d:ndims(x) 1:d-1]; 
z=reshape(permute(x,p),n,prod(s)/n); 
 
y=max(z); 
y=y+log(sum(exp(z-y(ones(n,1),:)))); 
 
s(d)=1; 
y=ipermute(reshape(y,s(p)),p);