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Re: where() and IEEE NaN [message #17794 is a reply to message #17793]

Sat, 06 November 1999 00:00

Vincenzo Andretta
Messages: 1
Registered: November 1999

Junior Member

Try:

WHERE(FINITE(array,/NaN) eq 1)

Example:

IDL> array=[1.0,!VALUES.F_Infinity,-!VALUES.F_Infinity,!VALUES.F_ NaN]
IDL> print,where(finite(array) eq 0)
1 2 3
IDL> print,where(finite(array,/NaN) eq 1)
3
IDL> print,where(finite(array,/infinity) eq 1)
1 2

Note that IDL seems to be able to deal with "infinities", at least to some
extent:

IDL> print,min(array),max(array)
-Inf Inf
% Program caused arithmetic error: Floating illegal operand
IDL> print,1./array
1.00000 0.00000 -0.00000 NaN

I wouldn't rely on this behaviour, but it is conceivable one might want
to know where NaN values are, while ignoring infinities.

Vincenzo Andretta
CUA,NASA/GSFC - Laboratory for Astronomy and Solar Physics
Greenbelt, MD 20771 - USA

P.S:
IDL> help,/structure,!version
** Structure !VERSION, 5 tags, length=80:
ARCH STRING 'alpha'
OS STRING 'OSF'
OS_FAMILY STRING 'unix'
RELEASE STRING '5.2'
BUILD_DATE STRING 'Oct 30 1998'

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[Message index]

		Re: where() and IEEE NaN By: korpela on Mon, 08 November 1999 00:00
		Re: where() and IEEE NaN By: badastro on Mon, 08 November 1999 00:00
		Re: where() and IEEE NaN By: Pavel Romashkin on Mon, 08 November 1999 00:00
		Re: where() and IEEE NaN By: thompson on Mon, 08 November 1999 00:00
		Re: where() and IEEE NaN By: jsb on Thu, 11 November 1999 00:00
		Re: where() and IEEE NaN By: korpela on Sat, 06 November 1999 00:00
		Re: where() and IEEE NaN By: Vincenzo Andretta on Sat, 06 November 1999 00:00
		Re: where() and IEEE NaN By: davidf on Fri, 05 November 1999 00:00
		Re: where() and IEEE NaN By: davidf on Fri, 05 November 1999 00:00
		Re: where() and IEEE NaN By: Pavel Romashkin on Fri, 05 November 1999 00:00
		Re: where() and IEEE NaN By: thompson on Fri, 05 November 1999 00:00
		Re: where() and IEEE NaN By: T Bowers on Fri, 05 November 1999 00:00
		Re: where() and IEEE NaN By: badastro on Fri, 05 November 1999 00:00
		Re: where() and IEEE NaN By: davidf on Fri, 05 November 1999 00:00
		Re: where() and IEEE NaN By: korpela on Fri, 05 November 1999 00:00

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