find onest and end of wave ?

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yasmeen hadadd
yasmeen hadadd 2021-11-16
评论： Bjorn Gustavsson 2021-11-17
hello
how i can find the onest (the beginning) and the end of wave if i have the peaks only?
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KSSV
KSSV 2021-11-17
Show us how your data is. Pictorial example with your expectations will help us to help you.
yasmeen hadadd
yasmeen hadadd 2021-11-17
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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Bjorn Gustavsson
Bjorn Gustavsson 2021-11-17
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
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yasmeen hadadd
yasmeen hadadd 2021-11-17
yes yes yes
thank you very very much

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