Problem with function envelope

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Chiara Gigoli
Chiara Gigoli 2022-7-15
评论： Star Strider 2022-7-15
Hi,
I have a problem with function envelope. It worked for all my set of data but, in one case, it didn't. When a function become constant, the envelope "goes away", creating a sort of asymptote. Or better, I think that it works, but when the function become constant I have to change stategy or stop the envelope.
I put there a right plot, without envelope, and the plot in which I get this problem.
I use this code, for example:
[low_dMRe, up_dMRe] = envelope(Int_dMRe_20,3000,'peak');
Could anyone help me, please?
Thank you in advance
Chiara
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Chiara Gigoli
Chiara Gigoli 2022-7-15
Hi,
thank you very much for your answer.
Unfortunately, it doesn't work with my data...
But Star Strider gave me an helpful suggestion!
By the way, thank you a lot to give me this advice: it could be worth in other cases! :)
Chiara

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Star Strider
Star Strider 2022-7-15
Ran in:
The transition in the signal baselline is confusing envelope. It may be necessary to change the ‘np’ value, possibly to a lower number. I can reproduce the behaviour you’re seeing with different values, however with other values it comes close to behaving as expected. It will probably be necessary to just eliminate the envelope value above a specific time.
x = linspace(0, 10, 500);
y = exp(-1.25*x) .* sin(2*pi*x*4.5) + (1-exp(-0.5*x));
[envhi,envlo] = envelope(y, 46, 'peak');
figure
plot(x, y)
hold on
patch([x flip(x)], [envhi flip(envlo)], 'g', 'FaceAlpha',0.5, 'EdgeColor','none')
hold off
grid
title('Original')
ylim([-1 1.5])
Lv = envlo < y; % Plot 'envelope' Only When 'envlo' Is Less Than The Signal
figure
plot(x, y)
hold on
% plot(x, envhi, '-r')
patch([x(Lv) flip(x(Lv))], [envhi(Lv) flip(envlo(Lv))], 'g', 'FaceAlpha',0.5, 'EdgeColor','none')
hold off
grid
title('Limited')
ylim([-1 1.5])
Something like this should also work for your signal.
.
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Chiara Gigoli
Chiara Gigoli 2022-7-15
It perfectly worked!
Thank you so so much!
Chiara Gigoli

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