delay in digital filtering

Hi all.... I have an ECG signal need to be filtered with band pass filter, but the yielded signal after being filtered is flattened at early samples, why is that? and how to fix it?

Answer 1

[Wayne King]

One thing you can try is using filtfilt()

You have not given specifics about what kind of filter you used and how long your filter is in relation to your signal, but if you look at the reference page for filtfilt

https://www.mathworks.com/help/signal/ref/filtfilt.html

You'll see an example with a simulated ECG waveform that demonstrates the zerophase filtering that gets rid of the delay.