create an envelop for one oscillating curve

Hello, I have a data set for a displacement response of vibrating body. I need to characterize the decay increment of it. As initial step I need to know the function of the curve that envelop that response. It looks like this:

So I need to fined a function that passes through the tip points. NOTE: The data is a signal output, that is mean it is not smooth and have spikes! Thanks,

Answer 1

[Greg Dionne]

If you have the Signal Processing Toolbox, try ENVELOPE.

[Alaa Hameed]

Thanks Greg ... I will