Date: Feb 11, 2013 4:51 PM
Author: Derek Goring
Subject: Re: spectral derivation of aperiodic function
On Tuesday, February 12, 2013 9:15:43 AM UTC+13, Eileen Tudaleft wrote:

> bouloumag disgorged this amusing substitute for thought:

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> > I would like to calculate the spatial derivative of a variable defined

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> > on the points of a uniform grid. The domain is NOT periodic, so the FFT

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> > method is useless here.

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> really?

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> Google: aperiodic FFT

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> About 179,000 results (0.22 seconds)

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>

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> so all of that is entirely wrong?

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> > I wonder if there exist other spectral methods

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> > to calculate the derivative on an aperiodic domain or if my only hope is

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> > to use the finite difference method?

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> no, it's likely your 'other hope' is to spend some time thinking more carefully about your problem(s).

Yes, I was bemused by this post also.

It implies that Kolmogorov's -5/3 law of turbulence and all other such work is rubbish.

Perhaps OP is confusing non-periodic with non-stationary?

FFT is not good for non-stationary data.