function [y,offset,scale] = ml_libsvmnorm(x)
%ML_LIBSVMNORM Normalize features for lib svm.
%   Y = ML_LIBSVMNORM(X) returns the normalized feature matrix of X. Each 
%   feature is normalized into the range [-1 1].
%   
%   [Y,OFFSET,SCALE] = ML_LIBSVMNORM(...) also returns the offset and scale to
%   normalize the features.
%   
%   See also

%   16-Jan-2007 Initial write T. Zhao
%   Copyright (c) 2007 Murphy Lab
%   Carnegie Mellon University
%
%   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 should have received a copy of the GNU General Public License
%   along with this program; if not, write to the Free Software
%   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
%   02110-1301, USA.
%   
%   For additional information visit http://murphylab.web.cmu.edu or
%   send email to murphy@cmu.edu


if nargin < 1
    error('Exactly 1 argument is required');
end

maxx = max(x,[],1);
minx = min(x,[],1);

scale = (maxx-minx)/2;
scale(scale==0) = 1;
x = ml_multrow(x,1./scale);
offset = -min(x,[],1)-1;
y = ml_addrow(x,offset);
offset = -offset.*scale;
