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
hello
how i can find the onest (the beginning) and the end of wave if i have the peaks only?
  2 Comments
KSSV
KSSV on 17 Nov 2021
Show us how your data is. Pictorial example with your expectations will help us to help you.
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.
HTH
  4 Comments
yasmeen hadadd
yasmeen hadadd on 17 Nov 2021
yes yes yes
thank you very very much
Bjorn Gustavsson
Bjorn Gustavsson on 17 Nov 2021
You're ever so welcome.

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