function [out] = filterIsoline(in,fs)
% Isoline filtration of ECG using decimation and interpolation
% (c) Jakub Kuzilek
% http://bio.felk.cvut.cz/~kuziljak/ E-mail: jakub.kuzilek@gmail.com
% Version: 1.0 Last update: 12/04/2013.
% (Version: 1.0, 12/04/2013)
%
%======================================================
%
% PURPOSE: This function removes isoline drift from ECG signal.
%
% MANDATORY INPUT ARGUMENTS
% in ..... input data Mx1, M - length of data (one lead)
% fs ..... sampling frequency in Hz
% OPTIONAL INPUT ARGUMENTS
% none
% OUTPUT ARGUMENTS
% out .... filtered data Mx1
%=========================================================
% in order to remove filter initial slope extend input
fin=[in(1:fs);in];
np = length(fin);
xd = decimate(fin,round(fs/20),'fir'); % decimation
lbx = medfilt1(xd,10); % median filtering - get isoline
lb = interp(lbx,round(fs/20)); % interpolation
out = fin-lb(1:np);
out(1:fs)=[]; % result