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Re: Speedy way to get compare array elements. . . [message #32835 is a reply to message #32828]

Wed, 13 November 2002 20:28

Craig Markwardt
Messages: 1869
Registered: November 1996

Senior Member

"Sean Raffuse" <sean@me.wustl.edu> writes:
> Exalted newsgroup,
>
> What is the fastest way to compare two adjacent values in an array?
>
> Something like:
>
> whoa_huge_jump = where(A[i+1]-A[i] GT 500)

I usually use this little bit of magic,

whoa_huge_jump = where(A[1:*]-A GT 500)

Now, if you are a goody goody, the correct way to do the subtraction
is A[1:*]-A[0:N-2], but that can get annoying, especially if you have
to figure out N first. The cool thing about the trick is that IDL
*automatically* truncates the vector A so that it matches the length
of A[1:*].

Some people on the newsgroup thing it is too obscure, but heck, I have
to have something to distinguish my own style.

Craig

--
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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: Speedy way to get compare array elements. . . By: Pavel A. Romashkin on Thu, 14 November 2002 08:51
		Re: Speedy way to get compare array elements. . . By: Craig Markwardt on Wed, 13 November 2002 20:28
		Re: Speedy way to get compare array elements. . . By: the_cacc on Thu, 28 November 2002 06:58
		Re: Speedy way to get compare array elements. . . By: marc schellens[1] on Tue, 03 December 2002 22:54

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