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Re: Philosophical Question about NAN [message #63759 is a reply to message #63742]

Mon, 17 November 2008 07:54

wlandsman
Messages: 743
Registered: June 2000

Senior Member

On Nov 17, 9:58 am, David Fanning <n...@dfanning.com> wrote:
> Folks,
>
> I've had a couple of run-ins lately with NANs and I wonder
> why routines like TOTAL and MEAN don't have the NAN keyword
> set to 1 by default. Why does the user have to set it?

I agree with the sentiment but also note that always setting /NAN
incurs a non-trivial performance penalty, e.g.

IDL> a = randomn(seed,10000,2000)
IDL> t = systime(1) & b = total(a) & print,systime(1)-t
0.25451803
IDL> t = systime(1) & b = total(a,/nan) & print,systime(1)-t
0.35278893

I've thought at times that arrays should carry a hidden bit saying
whether or not they include NaN values, but this introduces other
overhead problems.

--Wayne

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[Message index]

		Re: Philosophical Question about NAN By: Foldy Lajos on Wed, 19 November 2008 08:09
		Re: Philosophical Question about NAN By: R.G. Stockwell on Wed, 19 November 2008 06:32
		Re: Philosophical Question about NAN By: R.Bauer on Tue, 18 November 2008 12:55
		Re: Philosophical Question about NAN By: pgrigis on Tue, 18 November 2008 08:42
		Re: Philosophical Question about NAN By: Jeremy Bailin on Tue, 18 November 2008 05:05
		Re: Philosophical Question about NAN By: R.Bauer on Tue, 18 November 2008 00:18
		Re: Philosophical Question about NAN By: pgrigis on Mon, 17 November 2008 17:07
		Re: Philosophical Question about NAN By: R.Bauer on Mon, 17 November 2008 16:38
		Re: Philosophical Question about NAN By: Kenneth P. Bowman on Mon, 17 November 2008 07:32
		Re: Philosophical Question about NAN By: wlandsman on Mon, 17 November 2008 08:28
		Re: Philosophical Question about NAN By: David Fanning on Mon, 17 November 2008 08:02
		Re: Philosophical Question about NAN By: Rainer on Mon, 17 November 2008 08:01
		Re: Philosophical Question about NAN By: wlandsman on Mon, 17 November 2008 07:54
		Re: Philosophical Question about NAN By: Mark[1] on Wed, 19 November 2008 16:24

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