MATLAB: How to improve detrending

arrhythmiabiomedical signal processingdetrendecg

Code:
d=load('CU_Ventricular_Tacharrhythmia\cu01m.mat');
noisyECG_withTrend=d.val(1,:);
subplot(2,1,1), plot(noisyECG_withTrend), grid on,
nnoisyECG_withTrend = noisyECG_withTrend';
t = 1:length(noisyECG_withTrend);
[p,s,mu] = polyfit((1:numel(noisyECG_withTrend))',nnoisyECG_withTrend,6)
f_y = polyval(p,(1:numel(noisyECG_withTrend))',[],mu);
ECG_data = nnoisyECG_withTrend - f_y;    % Detrend data
subplot(2,1,2), plot(t,ECG_data); grid on
%ax = axis; 
%axis([ax(1:2) -1.2 1.2])
title('Detrended ECG Signal')
xlabel('Samples'); ylabel('Voltage(mV)')
legend('Detrended ECG Signal')
Code Source: http://www.mathworks.com/help/signal/examples/peak-analysis.html

Best Answer

See if this filter does what you want (assuming Fs=256):
Fs = 256;
Fn = Fs/2;
Wp = [1 90]/Fn;
Ws = Wp.*[0.5 1.25];
Rp =  1;
Rs = 20;
[n,Wn] = buttord(Wp,Ws,Rp,Rs);
[b,a] = butter(n,Wn);
[sos,g] = tf2sos(b,a);
figure(1)
freqz(sos, 2048, Fs);
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