Filtering two channels ECG signals with sampling frequency of 1000 Hz using MATLAB

Hello,

I have got my data set of values for Two Channels ECG Signals, but am new to MATLAB and i dont know how to filter it. I think i must be using Digital Signal Processing methods, because the data set are of discrete values (.mat tables)

Thanks

Answer 1

[Star Strider]

The usual way of filtering EKG signals is to use a bandpass filter with a passband frequency of 2 to 100 Hz, and a stopband of 2 to 110 Hz. That should produce a stable filter. My filter design procedure is here: How to design a lowpass filter for ocean wave data in Matlab?

This designs a stable filter that should do what you want (eliminate base line wander and d-c offset, and high-frequency noise):

Fs = 1000;                                          % Sampling Frequency
Fn = Fs/2;                                          % Nyquist Frequency
Wp = [1.5  100]/Fn;                                 % Normalised Passband
Ws = [0.1  120]/Fn;                                 % Normalised Stopband
Rp = 20;                                            % Passband Ripple (dB)
Rs = 30;                                            % Stopband Ripple (dB)
[n,Wn] = buttord(Wp,Ws,Rp,Rs);                      % Filter Order
[b,a] = butter(n,Wn);                               % Filter Coefficients
[sos,g] = tf2sos(b,a);                              % Second-Order-Section For Stability

figure(1)
freqz(sos, 4096, Fs)                                % Filter Bode Plot

Use the filtfilt function with ‘sos’ and ‘g’ to filter your EKG signal.

[Mohanad Ahmed]

Thats good, but how can i apply this filter to my Data set that i got ?

[Star Strider]

Use the filtfilt function with ‘sos’ and ‘g’ to filter your EKG signal:

Filtered_EKG = filtfilt(sos, g, EKG);

[Mohanad Ahmed]

Am not really expert on this, but am still learning, I do have the two channels ECG signal data set (2x316000), plus ticktimes (1x316000) and range (1x316000) data sets. How can i filter the ECG signal out from this data ? i tried your code but it always gives me the same graph

[Star Strider]

I have no idea what your ‘ticktimes’ and ‘range’ data are or what you are doing.

I designed the standard EKG pre-processing filter everyone asks for, to filter out baseline offset and drift, and high-frequency noise. If your data have none of those, the output will be approximately the same as the input.

Your two-channel EKG data set are your EKG signals. There is nothing to ‘filter out’.