find onest and end of wave ?

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yasmeen hadadd
yasmeen hadadd on 16 Nov 2021
Commented: Bjorn Gustavsson on 17 Nov 2021
how i can find the onest (the beginning) and the end of wave if i have the peaks only?
yasmeen hadadd
yasmeen hadadd on 17 Nov 2021
Thnk you for replying :)
if i have an ecg signal and i find the peaks of every wave and i will find the onest and end of each wave , please see the figure bellow

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Answers (1)

Bjorn Gustavsson
Bjorn Gustavsson on 17 Nov 2021
You cannot in a strict sense. You will have to settle for the first and last wave-crest, or set some arbitrary threshold for the wave-amplitude (10% of the peak, of the peak-to-peak, whatever). That this is impossible follows from the fact that functions like f(x-vt) solves the wave-equation - we can for example set f to be some sequence of Gaussian pulses moving to the right, and since a Gaussian has infinite support where it starts or ends becomes a question of where you set your threshold.
In practice if you have some natural noise-level in your measurements this might give you some sensible reason to select a threshold.
Bjorn Gustavsson
Bjorn Gustavsson on 17 Nov 2021
You're ever so welcome.

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