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Re: Butterworth Band-Pass Filter [message #73912 is a reply to message #73911]

Sun, 12 December 2010 09:07

burton449
Messages: 15
Registered: December 2010

Junior Member

On Dec 12, 12:02 pm, David Fanning <n...@dfanning.com> wrote:
> burton449 writes:
>> According to your documentation, a high-pass butterworth filter will
>> be defined like that:
>> filter = 1 / [1 + C(Ro/R)^2n]
>
>> So in IDL, for a cuttoff of 15, and freqImage = FFT(image, -1), the
>> filter will be defined like that:
>> filter = 1.0 / ( 1.0d + (15.0/freqImage)^2 )
>
>> Is it right?
>
> For what it's worth, I got confused by all this when
> I was reading this article, too, in preparation for
> including this information in my new book. I think I
> explained it better in the book, and I'll probably go
> back and fix this article, too. But not now. I can see
> the end of this book from where I am standing and I am
> at the point where bathing is completely extraneous to
> my purpose! :-)
>
> Cheers,
>
> David
>
> --
> David Fanning, Ph.D.
> Fanning Software Consulting, Inc.
> Coyote's Guide to IDL Programming:http://www.dfanning.com/
> Sepore ma de ni thui. ("Perhaps thou speakest truth.")

Is it possible to have a look at this book? :)

I dont think you can create a High-Pass filter the way you explain it
like your last post or like you explain in the article because you
have the division by 0 error when you put the Dist function in
denominator... even in your example with dist(248) you have the same
error...

Max

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[Message index]

		Re: Butterworth Band-Pass Filter By: David Fanning on Sun, 12 December 2010 09:24
		Re: Butterworth Band-Pass Filter By: David Fanning on Sun, 12 December 2010 09:19
		Re: Butterworth Band-Pass Filter By: burton449 on Sun, 12 December 2010 09:07
		Re: Butterworth Band-Pass Filter By: David Fanning on Sun, 12 December 2010 09:02
		Re: Butterworth Band-Pass Filter By: David Fanning on Sun, 12 December 2010 08:56
		Re: Butterworth Band-Pass Filter By: burton449 on Sun, 12 December 2010 08:29
		Re: Butterworth Band-Pass Filter By: David Fanning on Sat, 11 December 2010 20:37
		Re: Butterworth Band-Pass Filter By: burton449 on Sun, 12 December 2010 09:28
		Re: Butterworth Band-Pass Filter By: burton449 on Sun, 12 December 2010 09:30

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