function xfilt = medianfilter(x, freq)
% FilterForTWA.m
% Author: Alexander Khaustov; alexander dot khaustov at gmail dot com
% Copyright (C) 2008 St.-Petersburg Institute of Cardiological Technics (Incart), www.incart.ru
% This software is released under the terms of the GNU General
% Public License (http://www.gnu.org/copyleft/gpl.html).
%
% Simple median filtration to remove baseline wander
freqd = 32;
factor = floor(freq / freqd);
y = x(1:factor:length(x));
halfwindclassic = floor(1.3 * freqd / 2);
m = zeros(1,length(y));
for i = 1 : length(y)
clear ss
pstartc = max((i - halfwindclassic), 1);
pendc = min((i + halfwindclassic), length(y));
ss = sort(y(pstartc : pendc));
m(i) = mean(ss(floor(0.375 * length(ss)) : floor(0.625 * length(ss))));
end;
res = zeros(1, length(x));
for i = 1:length(x)
res(i) = m(floor((i-1) / factor) + 1);
end;
xfilt = x - res';
return;