function [ect_loc] = ectopic_detection(Rpos)
% Input
% Rpos - Position of the R peaks
%
% Output
% ect_loc - Position of the ectopic peaks. Used for respiration analysis
%
% Author(s): Jonathan Moeyersons (Jonathan.Moeyersons@esat.kuleuven.be)
% Sabine Van Huffel (Sabine.Vanhuffel@esat.kuleuven.be)
% Carolina Varon (Carolina.Varon@esat.kuleuven.be)
%
% Version History:
% - 17/02/2019 JM Initial version
%
% Copyright (c) 2019, Jonathan Moeyersons, KULeuven-ESAT-STADIUS
%
% This software is made available for non commercial research purposes only
% under the GNU General Public License. However, notwithstanding any
% provision of the GNU General Public License, this software may not be
% used for commercial purposes without explicit written permission after
% contacting jonathan.moeyersons@esat.kuleuven.be
%
% 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 3 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, see <https://www.gnu.org/licenses/>.
% Set basic variables
a = 0.1; % 10% difference
b = 0.05; % 5% difference
max_k = 5; % Maximum ammount of previous RR-intervals
% Get the RR-intervals
RR = diff(Rpos);
% Get the amount of RR-intervals
len = length(RR);
% Pre-allocate
RRref_all = zeros(1,len); % Reference RR intervals
ectopic = zeros(1,len); % Index of ectopics
% Set first RR-reference
RR_ref = median(RR(1:max_k));
RRref_all(1) = RR_ref;
% Set loop start
counter = 1;
% Loop over the different RR-intervals
while counter < len-1
% Define the RR-ref if you are further than the first RR-interval
if counter > 2
% Set variables
k = 1; % Number of previous RR-intervals
sum_ref = 0; % Sum of the good previous RRI's
num = 0; % Number of good previous RRI's
wght = [0.5 0.3 0.2]; % Weights: the farther away, the lower the weight
while counter-k > 0 && num < 3 && k < max_k
% Check if the previous RRI is an ectopic
if ectopic(counter-k) == 1
prob_check = 1;
elseif ectopic(counter-k) == 0
prob_check = 0;
end
% If this is not the case, use it for reference
if ~prob_check
num = num + 1;
sum_ref = sum_ref + wght(num)*RR(counter-k);
end
k = k+1;
end
% If no good previous RR-intervals are found, this probably means that
% this is the new normal, so just take the three previous
if num <= 1
k = 1;
while counter-k > 0 && num < 3
num = num + 1;
sum_ref = sum_ref + wght(num)*RR(counter-k);
k = k+1;
end
end
% Define the reference variables
RR_ref = sum_ref/sum(wght(1:num));
no_RR_ref = nnz(RRref_all);
RRref_all(no_RR_ref+1) = RR_ref;
end
% Check for ectopics
if ((RR(counter) < (1-a)*RR_ref) && (RR(counter+1) > (1+b)*RR_ref)) ||...
((RR(counter) > (1+b)*RR_ref) && (RR(counter+1) < (1-a)*RR_ref))
% Indicate the presence of an ectopic
ectopic(counter) = 1;
end
% Add to the counter
counter = counter + 1;
end
% Define the ectopic locations
ect_loc = find(ectopic == 1)+1;