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envelope of an oscillatory InterpolatingFunction

  • To: mathgroup at
  • Subject: [mg49780] envelope of an oscillatory InterpolatingFunction
  • From: "Stergios J. Papadakis" <stergios.papadakis at>
  • Date: Sat, 31 Jul 2004 03:14:00 -0400 (EDT)
  • Organization: Johns Hopkins University Applied Physics Lab, Laurel, MD, USA
  • Sender: owner-wri-mathgroup at

Dear group,
I use NDSolve and get an oscillatory
InterpolatingFunction with a slowly
varying envolope.  I would like to
extract just the envelope.  Right
now I am FFTing the InterpolatingFunction,
using NMaximize to find the peak and
therefore the carrier frequency.
Then I step through the InterpolatingFunction
using a While loop, one period at a time,
and use NMaximize to find the maximum on
that each period.  This is really slow, and sometimes
it just obviously gets it wrong and I can't
really figure out why.

Is there a better way that I just don't know about?


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