Daniel@0: function y=logsum(x,d)
Daniel@0: %LOGSUM logsum(x,d)=log(sum(exp(x),d))
Daniel@0: %  d gives dimension to sum along
Daniel@0: 
Daniel@0: %      Copyright (C) Mike Brookes 1998
Daniel@0: %
Daniel@0: %      Last modified Mon Oct 12 15:47:25 1998
Daniel@0: %
Daniel@0: %   VOICEBOX is a MATLAB toolbox for speech processing. Home page is at
Daniel@0: %   http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html
Daniel@0: %
Daniel@0: 
Daniel@0: if nargin==1
Daniel@0:    d=[find(size(x)-1) 1];
Daniel@0:    d=d(1);
Daniel@0: end
Daniel@0: n=size(x,d);
Daniel@0: if n<=1, y=x; return; end
Daniel@0: s=size(x);
Daniel@0: p=[d:ndims(x) 1:d-1];
Daniel@0: z=reshape(permute(x,p),n,prod(s)/n);
Daniel@0: 
Daniel@0: y=max(z);
Daniel@0: y=y+log(sum(exp(z-y(ones(n,1),:))));
Daniel@0: 
Daniel@0: s(d)=1;
Daniel@0: y=ipermute(reshape(y,s(p)),p);
Daniel@0: