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Re: Incorrect behavior of /NAN [message #30027 is a reply to message #30025]

Thu, 04 April 2002 09:32

Craig Markwardt
Messages: 1869
Registered: November 1996

Senior Member

Kenneth Bowman <k-bowman@null.tamu.edu> writes:
> I tried to incite some interest in this last week, but had no takers,
> so I'll try again. ;-)
>
> I believe that the behavior of the TOTAL function is incorrect in
> the case where all of the data are NaN and the /NAN keyword is set.
>
> Here are several possible cases:
>
> IDL> a = !values.f_nan
> IDL> print, total([a, 1.0])
> NaN
> IDL> print, total([a, 1.0], /nan)
> 1.00000
> IDL> print, total([a, a])
> NaN
> IDL> print, total([a, a], /nan)
> 0.00000
>
> I believe that the last case is incorrect.
>
> The documentation for /NAN says "Elements with the value NaN are treated
> as missing data." In the last case there are no valid data, so how can
> their sum be zero?

Hi Ken--

If all the data are missing, how can the sum be NaN? Neither a return
value of 0, nor a return value of NaN, seems to be appropriate to
me. This appears to be an undefined case.

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: Incorrect behavior of /NAN By: Paul van Delst on Thu, 04 April 2002 11:38
		Re: Incorrect behavior of /NAN By: Jaco van Gorkom on Thu, 04 April 2002 10:38
		Re: Incorrect behavior of /NAN By: Paul van Delst on Thu, 04 April 2002 10:19
		Re: Incorrect behavior of /NAN By: Craig Markwardt on Thu, 04 April 2002 09:32
		Re: Incorrect behavior of /NAN By: K. Bowman on Fri, 05 April 2002 10:20
		Re: Incorrect behavior of /NAN By: Mark Hadfield on Thu, 04 April 2002 13:06
		Re: Incorrect behavior of /NAN By: Craig Markwardt on Thu, 04 April 2002 18:26

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