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Re: IDL 4.0.1, best way to deal with missing/bad data [message #5818 is a reply to message #5783]

Thu, 22 February 1996 00:00

f055
Messages: 29
Registered: April 1995

Junior Member

->>>>> "Bill" == William Thompson <thompson@orpheus.nascom.nasa.gov> writes:
Bill> The trouble with using NaN values is ......... <cut>

Another problem with NaN is (I've just discovered to my cost) that there's
no way to represent it in integer or long variables - only double or floats.

I've been using NaN since upgrading to IDL4, and have just realised an error
in a couple of my programs: I read in a dataset, set all missing data to
!values.f_nan. Then, to replicate someone else's results who did some
analysis with a precision of 1 decimal place, I rounded all my values to
1 d.p. with:

fd = float( round( fd*10. ) ) / 10.

The round, of course, altered all values to integer and set all !values.f_nan
to zeros, which I then converted back to floats. I never noticed, oops.
If I'd known, I could've kept a copy of the original fd and used that to
remask the new fd where appropriate. But even so, I'm sure some applications
would want to use data as ints or longs with some kind of missing code.

......................... Dr Tim Osborn . t.osborn@uea.ac.uk
.... ___/.. __ /.. /.. /. Senior Research Associate . phone:01603 592089
... /..... /. /.. /.. /.. Climatic Research Unit . fax: 01603 507784
.. /..... __/.. /.. /... School of Environmental Sciences.
. /..... /\ ... /.. /.... University of East Anglia .
____/.._/..\_..____/..... Norwich NR4 7TJ .
......................... UK .

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[Message index]

		IDL 4.0.1, best way to deal with missing/bad data By: rfinch on Fri, 09 February 1996 00:00
		Re: IDL 4.0.1, best way to deal with missing/bad data By: f055 on Thu, 22 February 1996 00:00
		Re: IDL 4.0.1, best way to deal with missing/bad data By: rfinch on Mon, 19 February 1996 00:00
		Re: IDL 4.0.1, best way to deal with missing/bad data By: thompson on Sat, 17 February 1996 00:00

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