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Re: Negative indexing and the WHERE function in IDL 8.0 [message #72175 is a reply to message #72166]

Wed, 18 August 2010 09:31

chris_torrence@NOSPAM is currently offline

chris_torrence@NOSPAM
Messages: 528
Registered: March 2007

Senior Member

Hi all,

A possible solution is to use the new /NULL keyword to WHERE:

data = [1,2,3,4]
data[WHERE(data eq 5, /NULL)] = 999
print, data
1 2 3 4

If /NULL is set, and there are no matches, then WHERE returns the new !
NULL "empty array". In IDL 8.0, if you are indexing into an array, and
any of the subscripts are !NULL, then the indexing is quietly skipped.

This solution still requires you to examine your old code carefully
and retrofit it, but it's a lot easier to add a /NULL to your WHERE
calls than to implement the error handling for the -1.

Hope this helps.

-Chris
ITTVIS

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[Message index]

		Re: Negative indexing and the WHERE function in IDL 8.0 By: wlandsman on Thu, 19 August 2010 06:29
		Re: Negative indexing and the WHERE function in IDL 8.0 By: svhhaugan on Thu, 19 August 2010 05:09
		Re: Negative indexing and the WHERE function in IDL 8.0 By: chris_torrence@NOSPAM on Wed, 18 August 2010 09:31
		Re: Negative indexing and the WHERE function in IDL 8.0 By: svhhaugan on Fri, 20 August 2010 03:36
		Re: Negative indexing and the WHERE function in IDL 8.0 By: Greg Hennessy on Thu, 19 August 2010 18:35
		Re: Negative indexing and the WHERE function in IDL 8.0 By: penteado on Thu, 19 August 2010 11:02

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