matthiasm@8: function y=logsum(x,d)
matthiasm@8: %LOGSUM logsum(x,d)=log(sum(exp(x),d))
matthiasm@8: %  d gives dimension to sum along
matthiasm@8: 
matthiasm@8: %      Copyright (C) Mike Brookes 1998
matthiasm@8: %
matthiasm@8: %      Last modified Mon Oct 12 15:47:25 1998
matthiasm@8: %
matthiasm@8: %   VOICEBOX is a MATLAB toolbox for speech processing. Home page is at
matthiasm@8: %   http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html
matthiasm@8: %
matthiasm@8: 
matthiasm@8: if nargin==1
matthiasm@8:    d=[find(size(x)-1) 1];
matthiasm@8:    d=d(1);
matthiasm@8: end
matthiasm@8: n=size(x,d);
matthiasm@8: if n<=1, y=x; return; end
matthiasm@8: s=size(x);
matthiasm@8: p=[d:ndims(x) 1:d-1];
matthiasm@8: z=reshape(permute(x,p),n,prod(s)/n);
matthiasm@8: 
matthiasm@8: y=max(z);
matthiasm@8: y=y+log(sum(exp(z-y(ones(n,1),:))));
matthiasm@8: 
matthiasm@8: s(d)=1;
matthiasm@8: y=ipermute(reshape(y,s(p)),p);
matthiasm@8: