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Topic: spectral derivation of aperiodic function
Replies: 2   Last Post: Feb 11, 2013 5:37 PM

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Derek Goring

Posts: 3,892
Registered: 12/7/04
Re: spectral derivation of aperiodic function
Posted: Feb 11, 2013 4:51 PM
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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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>
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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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>
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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.



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