preprocessingNew

preprocessingNew Pre-processing of ECG signal
 Pre-processing using normalization and filtering.

 Process:
   1. Each second was detrended by removing the mean from each sample and
      dividing by the standard deviation.
   2. The signal is then band-passed filtered at 16Hz-26Hz using a
      butterworth filter.

 Inputs:
    sig - The raw ECG
    fs - The sampling frequency

 Outputs:
    sig - The preprocessed signal
    detrended - The signal after the first step only (no time shifting).


 Reference:
 Kota, S., Swisher, C.B. & al (2017). "Identification of QRS complex in
 non-stationary electrocardiogram of sick infants."
 Computers in Biology and Medicine 87 (2017) 211–216

0001 function [ sig, detrended ] = preprocessingNew(sig, fs)
0002 %preprocessingNew Pre-processing of ECG signal
0003 % Pre-processing using normalization and filtering.
0004 %
0005 % Process:
0006 %   1. Each second was detrended by removing the mean from each sample and
0007 %      dividing by the standard deviation.
0008 %   2. The signal is then band-passed filtered at 16Hz-26Hz using a
0009 %      butterworth filter.
0010 %
0011 % Inputs:
0012 %    sig - The raw ECG
0013 %    fs - The sampling frequency
0014 %
0015 % Outputs:
0016 %    sig - The preprocessed signal
0017 %    detrended - The signal after the first step only (no time shifting).
0018 %
0019 %
0020 % Reference:
0021 % Kota, S., Swisher, C.B. & al (2017). "Identification of QRS complex in
0022 % non-stationary electrocardiogram of sick infants."
0023 % Computers in Biology and Medicine 87 (2017) 211–216
0024 
0025 
0026 % every second of the ECG signal was normalized by the standard deviation of the signal in that second.
0027 numSecs = floor(length(sig) / fs);
0028 sigFullSecs = sig(1:numSecs*fs);
0029 sigSplit = reshape(sigFullSecs, fs, numSecs);
0030 newsig = sigSplit;
0031 
0032 parfor i = 1:numSecs
0033     currSec = sigSplit(:,i);
0034     M = mean(currSec);
0035     S = std(currSec);
0036     normalizedSec = arrayfun(@(a) (a - M)/ S, currSec);
0037     newsig(:,i) = normalizedSec;
0038 end
0039 sigExtend = reshape(newsig,[],1);
0040 sig(1:length(sigExtend)) = sigExtend;
0041 
0042 % ECG was detrended using a 120-ms smoothing filter with a zero-phase distortion.
0043 sig(isnan(sig)) = 0;
0044 
0045 detrended = sig;
0046 
0047 f1=16; %cuttoff low frequency to get rid of baseline wander
0048 f2=26; %cuttoff frequency to discard high frequency noise
0049 Wn=[f1 f2]*2/fs; % cutt off based on fs
0050 N = 3; % order of 3 less processing
0051 [a,b] = butter(N,Wn); %bandpass filtering
0052 ecg_h = filtfilt(a,b,sig);
0053 sig = ecg_h/ max( abs(ecg_h));
0054 
0055