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Re: FFTs in IDL [message #5808 is a reply to message #5760]

Fri, 23 February 1996 00:00

Sergei Senin
Messages: 23
Registered: February 1996

Junior Member

Achim Hein <hein@maxwell.nv.et-inf.uni-siegen.de> wrote:

>>> skipped<<<
> -It is very important to know that there is a little mistake in the
> WAVE-Algorithm not in the IDL-Algorithm, try to plot test=findgen(4097)
> and oplot,fft(fft(test,-1),1) you will see what I mean.

Sorry, a I'm a bit late for this discussion, but nevertheless:

wave> test=findgen(4097)
wave> print, max(test-fft(fft(test,-1),1))
wave> ( 29.4698, 0.247685)

and:

wave> test=findgen(4096)
wave> print, max(test-fft(fft(test,-1),1))
wave> ( 0.0163574, -0.000450487)

There seems to be no mistake, but simply no check in the procedure for the
number of elements in the array being 2^X.

> -In my opinion zero padding is definitly not a stupid thing to do.

No, but sometimes painfull :-) Could REBIN help in doing this for 2D arrays?

> Achim Hein
> Center of Sensor Systems
> Remote Sensing and optimal Signal Processing
> University of Siegen
>

--
Sergei Senin
University of Portsmouth
Department of Electrical and Electronic Engineering
Microwave, Telecommunications and Signal Processing Research Group
Anglesea Building, Anglesea Road,
Portsmouth,P01 3DJ,England.
ss@ee.port.ac.uk, http://www.ee.port.ac.uk:80/~ss-www/

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[Message index]

		FFTs in IDL By: tom on Thu, 15 February 1996 00:00
		Re: FFTs in IDL By: Sergei Senin on Fri, 23 February 1996 00:00
		Re: FFTs in IDL By: Sergei Senin on Tue, 27 February 1996 00:00
		Re: FFTs in IDL By: Achim Hein on Tue, 27 February 1996 00:00
		Re: FFTs in IDL By: Sergei Senin on Tue, 27 February 1996 00:00
		Re: FFTs in IDL By: Achim Hein on Tue, 27 February 1996 00:00

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