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Author: Dacapi91

ECG-problem resample.png

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+%% Edge effect using resample
+
+% This script shows the edge effect due to resampling operation in signals.
+% In addition, it presents two alternatives to fix it.
+
+% Author: MSc. David Castro Piñol
+
+clear; close all; clc;
+load ecgSignal;
+Fs = 250;
+newFs = 360;
+
+n = 0:length(ecgSignal)-1;
+t1 = n*1/Fs;
+
+%% Problem Edge Effects
+
+signalResampled = resample(ecgSignal,newFs,Fs);
+n2 = 0:length(signalResampled)-1;
+t2 = n2*1/newFs;
+
+figure; plot(t1,ecgSignal,'b',t2,signalResampled,'r'); ylim([-4.7 -2.5]);
+xlabel('Time (s)'); ylabel('Signal'); legend('Original','Resampled', ...
+    'Location','NorthWest');
+
+%% First Alternative: mean normalization
+
+ecgSignalMeanOff = ecgSignal - mean(ecgSignal);
+signalResampled = resample(ecgSignalMeanOff,newFs,Fs);
+n2 = 0:length(signalResampled)-1;
+t2 = n2*1/newFs;
+
+figure; plot(t1,ecgSignalMeanOff,'bo-',t2,signalResampled,'r*-'); 
+xlabel('Time (s)'); ylabel('Signal'); legend('Zero Mean','Resampled', ...
+    'Location','NorthWest');
+
+%% Second Alternative: Flip and shift
+
+L = ceil(length(ecgSignal)*newFs/Fs);
+flipedSignal = [flip(ecgSignal);ecgSignal;flip(ecgSignal)];       
+signalResampled = resample(flipedSignal,newFs,Fs);
+
+figure; subplot(211);plot(signalResampled,'b'); title('Flip and Shift ECG signal');
+hold on; plot(L:2*L-1,signalResampled(L:2*L-1),'r'); 
+cutSignal = signalResampled(L:2*L-1);
+subplot(212);plot(t2,cutSignal,'r');  title('Cutting signal');
+
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