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Re: Is there no NULL in IDL?? [message #30842 is a reply to message #30839]

Mon, 20 May 2002 15:42

Wayne Landsman
Messages: 117
Registered: January 1997

Senior Member

Sean Raffuse wrote:

> Am I just blind? What can I use for a null value when my data type is
> integer? Please don't tell me zero.

I can think of 4 options, each of which might be best in particular
situations:

(1) Use a known "non-physical" value (e.g. -32767) to flag nulls. (But
be careful when applying numeric operations on the data .)

(2) Convert to floating point and use NAN values to represent nulls.

(3) Carry around an extra byte mask array indicating which pixels are
null.

(4) Carry around a "null pixel list" vector , i.e. a vector of 1-d
indicies indicating which pixels in the data are null.

--Wayne Landsman landsman@mpb.gsfc.nasa.gov

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[Message index]

		Re: Is there no NULL in IDL?? By: Sean Raffuse on Tue, 21 May 2002 10:29
		Re: Is there no NULL in IDL?? By: R.Bauer on Mon, 20 May 2002 23:10
		Re: Is there no NULL in IDL?? By: btupper on Mon, 20 May 2002 17:36
		Re: Is there no NULL in IDL?? By: Wayne Landsman on Mon, 20 May 2002 15:42

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