function idxRRtoBeRemoved = FindSpikesInRR(RR, th)
%
% idxRRtoBeRemoved = FidnSpikesInRR(RR, th)
%
% OVERVIEW : Code used to clean RR intervals that change more than a given
% threshold (eg., th = 0.2 = 20%) with respect to the median value of the
% pervious 5 and next 5 RR intervals (using a forward-backward approach).
%
% INPUTS:
% RR : a single row of rr interval data in seconds
% th : threshold percent limit of change from one interval to the next
% OUTPUTS:
% idxRRtoBeRemoved : a single vector of indexes related to RR
% intervals corresponding to a change > th
%
% DEPENDENCIES & LIBRARIES:
% PhysioNet Cardiovascular Signal Toolbox
% https://github.com/cliffordlab/PhysioNet-Cardiovascular-Signal-Toolbox
%
% REFERENCE:
% Vest et al. "An Open Source Benchmarked HRV Toolbox for Cardiovascular
% Waveform and Interval Analysis" Physiological Measurement (In Press), 2018.
%
% REPO:
% https://github.com/cliffordlab/PhysioNet-Cardiovascular-Signal-Toolbox
%
% Written by Giulia Da Poian (giulia.dap@gmail.com), 09-13-2017
%
% LICENSE:
% This software is offered freely and without warranty under
% the GNU (v3 or later) public license. See license file for
% more information
%
if size(RR,1)>size(RR,2)
RR = RR';
end
% Forward search
FiveRR_MedianVal = medfilt1(RR,5); % compute as median RR(-i-2: i+2)
% shift of three position to aligne with to corresponding RR
FiveRR_MedianVal = [RR(1:5) FiveRR_MedianVal(3:end-3)];
rr_above_th = find((abs(RR-FiveRR_MedianVal)./FiveRR_MedianVal)>=th);
RR_forward = RR;
RR_forward(rr_above_th) = NaN;
% Backward search
RRfilpped = fliplr(RR);
FiveRR_MedianVal = medfilt1(RRfilpped,5); % compute as median RR(-i-2: i+2)
% shift of three position to aligne with to corresponding RR
FiveRR_MedianVal = [RRfilpped(1:5) FiveRR_MedianVal(3:end-3)];
rr_above_th = find(abs(RRfilpped-FiveRR_MedianVal)./FiveRR_MedianVal>=th);
rr_above_th = sort(length(RR)-rr_above_th+1);
RR_backward = RRfilpped;
RR_backward(rr_above_th) = NaN;
% Combine
idxRRtoBeRemoved = (isnan(RR_forward) & isnan(RR_backward));
end