function Align = AlignBeats(ecg, beats, q, s, STLen)
% AlignBeats.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).
%
% Interprets results of FindFiducials and prints diagnostic messages
% INPUT:
% ecg ecg signal (could be multiple channels)
% beats number of analysis beats
% q location of q marks
% s location of s marks
% STlen ST interval segment length
%
% OUTPUT:
% Align: structure containing the fields:
% fid (1 x beats): empty when unsuccessful, fiducial
% points that maximize cross-correlation on ST interval
% fidQRS (1 x beats): empty when unsuccessful, fiducial
% points that maximize cross-correlation on QS interval
% amp (beats x leads): amplitudes to subtract to align beats vertically, leads = size(ecg, 2)
% q2f average estimate of interval between Q and fiducial points
% f2s average estimate of interval between fiducial points and S
% st equal to STLen
% valid (beats x leads): 1 if the beat correlation with template is acceptable both on QS and ST
% intervals in the specified lead, 0 otherwise
global Param;
Align.fid = [];
Align.valid = [];
Align.st = STLen;
Align = FindFiducials(ecg, q, s, Align);
if (isempty(Align.fid))
disp('no lead is suitable for alignment, finishing..');
return;
end;
for lead = 1:size(ecg, 2)
NInvalid = length(find(1 - Align.valid(:, lead)));
if NInvalid
s = sprintf('AlignBeats: %d invalid beats in lead %d', NInvalid, lead);
disp(s);
end;
end;
if (length(Align.fid) > beats)
Align.fid = Align.fid(1:beats);
end;
return;