function lo=lpcrf2lo(rf)
%LPCRF2LO Convert reflection coefficients to log area ratios LO=(RF)
%the output values are limited to about +-14.5


%      Copyright (C) Mike Brookes 1997
%
%      Last modified Tue May 12 16:18:28 1998
%
%   VOICEBOX home page: http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html
%
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%   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
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%   This program is distributed in the hope that it will be useful,
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%   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
%   GNU General Public License for more details.
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r=max(min(rf,1-1E-6),1E-6-1);
lo=log((1-r)./(1+r));