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Re: Convolution, IDL & Numerical Recipes [message #32677 is a reply to message #32676]

Thu, 31 October 2002 13:48

JD Smith
Messages: 850
Registered: December 1999

Senior Member

On Thu, 31 Oct 2002 13:50:29 -0700, Hector Aceves wrote:

> Hello..
>
> I am using IDL for some of my research and have a particular problem
> with convolution of two arrays. I have used IDL's CONVOL procedure and
> subroutine CONVLV given in NUMERICAL RECEIPES..both give different
> results. I hope some one can shed light on what the reason might be.

Because IDL's convol() really does a correlation, not a convolution at
all! In a true convolution, the kernel is reversed (rotated by 180
degrees). You could try z=convol(a,reverse(k)) to get a true
convolution for comparison.

JD

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[Message index]

		Re: Convolution, IDL & Numerical Recipes By: David Fanning on Fri, 01 November 2002 06:48
		Re: Convolution, IDL & Numerical Recipes By: R.G. Stockwell on Fri, 01 November 2002 06:09
		Re: Convolution, IDL & Numerical Recipes By: R.G. Stockwell on Fri, 01 November 2002 06:01
		Re: Convolution, IDL & Numerical Recipes By: Kenneth P. Bowman on Thu, 31 October 2002 19:41
		Re: Convolution, IDL & Numerical Recipes By: James Kuyper on Thu, 31 October 2002 17:10
		Re: Convolution, IDL & Numerical Recipes By: David Fanning on Thu, 31 October 2002 14:29
		Re: Convolution, IDL & Numerical Recipes By: JD Smith on Thu, 31 October 2002 13:48
		Re: Convolution, IDL & Numerical Recipes By: aceves on Mon, 04 November 2002 18:55
		Re: Convolution, IDL & Numerical Recipes By: David Fanning on Fri, 01 November 2002 06:53
		Re: Convolution, IDL & Numerical Recipes By: aceves on Fri, 01 November 2002 17:06

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