How to extract data from an array

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Peter Darrouj
Peter Darrouj 2022-3-11
回答： Benjamin Thompson 2022-3-11
Hello. I have a signal with over 10mil data points. Whenever my signal crosses a certain threshhold i want to extract x numbers of point before and x numbers of point after it hit the threshhold.
IsEvent = true;
peakthreshhold = 120;
for i = 1:1:length(sig)
if (sig(i) >= peakthreshhold && IsEvent)
signal= (sig(i-20000):1:sig(i+50000));
disp(signal)
IsEvent = false;
end
end
so basically i wanted to extract 20000 points before it hit sig(i) to 50000 after it hit sig(i), so i get a new array with 70000 points extracted from sig(i).
If i run it now, i get 15 points

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采纳的回答

Benjamin Thompson
Benjamin Thompson 2022-3-11
Use
signal= sig(i-20000:1:i+50000);
And you probably need checks in case i < 20000 or i > (end - 50000) as special cases.

更多回答（1 个）

KSSV
KSSV 2022-3-11
Let x be your signal and val be yout threshold.
val = 50000 ;
tol = 10^-3 ;
idx = find(abs(sig-val)<=tol) ; % this gives the index of your threshold
v1 = sig(1:idx) ;
v2 = sig(idx+1:end) ;
  1 个评论
Peter Darrouj
Peter Darrouj 2022-3-11
i changed
signal= (sig(i-20000):1:sig(i+50000));
to:
signal= sig((i-20000):(i+50000));
This seems to have fixed the problem.
I still need to test ur answer because it looks like an easier way, but i dont understand what you did.

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