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Re: Complications with variance using FFTs [message #40125 is a reply to message #40106]

Wed, 21 July 2004 11:30

Craig Markwardt
Messages: 1869
Registered: November 1996

Senior Member

olde_english33@hotmail.com (Eric) writes:
>
> From what I can gather from my program, the positive frequencies are
> those from 1:15. Then the frequencies from 16:30 are the complex
> conjugates of the frequencies from 15:1. Therefore, I thinkt that IDL
> is already accounting for the complex conjugate in the negative
> frequencies, unless I am missing something.

I think you are missing that when you multiply the positive frequency
components by a complex phase, then you must also multiply the
negative frequency components by the complex conjugate, i.e. the
negative of that phase. To preserve a real signal that is.

That's another probing question, is the final result of your technique
real or complex?

Craig

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Craig B. Markwardt, Ph.D. EMAIL: craigmnet@REMOVEcow.physics.wisc.edu
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
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[Message index]

		Re: Complications with variance using FFTs By: olde_english33 on Thu, 22 July 2004 10:06
		Re: Complications with variance using FFTs By: Craig Markwardt on Wed, 21 July 2004 11:30
		Re: Complications with variance using FFTs By: olde_english33 on Wed, 21 July 2004 10:53
		Re: Complications with variance using FFTs By: Craig Markwardt on Tue, 20 July 2004 06:54
		Re: Complications with variance using FFTs By: olde_english33 on Mon, 19 July 2004 09:19
		Re: Complications with variance using FFTs By: Craig Markwardt on Fri, 16 July 2004 14:21

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