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Re: Divide By Zero error [message #27884 is a reply to message #27878]

Fri, 09 November 2001 14:59

Craig Markwardt
Messages: 1869
Registered: November 1996

Senior Member

"Logan Lindquist" <llindqusit@mrdoc.cc> writes:

> This is a multi-part message in MIME format.
>
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> Does anyone know what the minum window size is for the fft function? =
> Does it have to be divisble by a certain number? I am getting 0's with a =
> 8x8 array. The array is pretty flat and dark [all around pixel value of =
> 50] but I wouldn't think that I should get zero's returned as a =
> frequency component.=20
>
> The solution that I see is to check to see if there are zero's in the =
> array and then either change them to 0.1 or skip that array when trying =
> to display it. [with a note to the user letting them know that no =
> frequency component can be found.]
>
> Hopefully someone will read this! I am going to try calling RSI to see =
> if they have an answer.=20

Logan, the usual way fourier power is defined, is the *squared
magnitude* of the fourier coefficients.

If you define

power = -alog10( abs(f)^2 )

then I think your problems will be alleviated.

Craig

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

		Re: Divide By Zero error By: Logan Lindquist on Sat, 10 November 2001 14:10
		Re: Divide By Zero error By: Logan Lindquist on Sat, 10 November 2001 14:06
		Re: Divide By Zero error By: Craig Markwardt on Fri, 09 November 2001 14:59
		Re: Divide By Zero error By: Logan Lindquist on Thu, 08 November 2001 07:37
		Re: Divide By Zero error By: Logan Lindquist on Wed, 07 November 2001 13:25
		Re: Divide By Zero error By: Nigel Wade on Fri, 09 November 2001 01:34
		Re: Divide By Zero error By: Stein Vidar Hagfors H[1] on Mon, 12 November 2001 08:52
		Re: Divide By Zero error By: Paul Manusiu on Thu, 08 November 2001 21:24
		Re: Divide By Zero error By: Paul Manusiu on Tue, 13 November 2001 17:57

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