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Re: idl and pv-wave [message #7928 is a reply to message #412]

Fri, 24 January 1997 00:00

Achim Hein
Messages: 42
Registered: February 1996

Member

decre wrote:
>
> Achim Hein wrote:
>>
>> Matt Delaney wrote:
>>>
>> In my opinion IDL allows more powerful tools especially graphic
>> input/output-tools additionally there are some little mistakes in the
>> WAVE/FFT algorithm.
>>
>> Achim
>>
>> _______________________________________________
>>
>
> Wooops !
> I'm new to pv-wave and intend to use it for fft, a.o.
> Can you comment on those _little_ mistakes in the WAVE/FFT ?
>
> Many thanks,
> Michel Decre
>
Try the following:
wave>test=findgen(4097)
wave>print,max(test-fft(test,-1),1))
wave>(31.3898,0.350983)

In IDL you will get as result:
IDL>test=findgen(4097)
IDL>print,max(test-fft(test,-1),1))
IDL>(0.000244141,1.39110e-05)

If you try to evaluate this FFT with a 4096-length, the results in both
programs are quite equal.

There was a discussion some month ago with Sergei Senin...:
In his opinion:
> <There seems to be no mistake, but simply no check in the procedure <for the number of elements in the array being 2^X.
But I think:
> It seems so, but I think a Fourier-Transform-Algorithm has to
> run for every array length

> <No, it shouldn't (at least in what is called classical FFT) - but a
<*programme*, based on the algorithm should.
> <Sergei Senin
> <ss@ee.port.ac.uk, http://www.ee.port.ac.uk:80/~ss-www/

Is there any 'mistake'-archive for IDL/WAVE?
_______________________________________________

Dipl.-Ing. A. Hein
PB2 / ZESS - Uni-GH-Siegen
Paul-Bonatz Str. 9-11
57068 Siegen
Phone: 0271/740-3362
Fax: 0271/740-2336
_______________________________________________

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[Message index]

		IDL and PV-Wave By: ritscher on Fri, 21 August 1992 06:39
		Re: idl and pv-wave By: Achim Hein on Thu, 23 January 1997 00:00
		Re: idl and pv-wave By: Achim Hein on Mon, 27 January 1997 00:00
		Re: idl and pv-wave By: Big Brother on Sat, 25 January 1997 00:00
		Re: idl and pv-wave By: brian.jackel on Fri, 24 January 1997 00:00
		Re: idl and pv-wave By: Achim Hein on Fri, 24 January 1997 00:00
		Re: idl and pv-wave By: decre on Thu, 23 January 1997 00:00

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