comp.lang.idl-pvwave archive: archive » Re: BYTSCL and NAN keyword

Home » Public Forums » archive » Re: BYTSCL and NAN keyword

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: BYTSCL and NAN keyword [message #38281 is a reply to message #38280]

Tue, 02 March 2004 09:13

Edd Edmondson
Messages: 50
Registered: January 2003

Member

Kenneth Bowman <k-bowman@null.tamu.edu> wrote:
> Has anyone else noticed this problem with BYTSCL and the NAN keyword?

> The BYTSCL function scales integers and floats into bytes between 0 and
> 255 (or the value set by the TOP keyword). If the NAN keyword is set,
> NANs in the input array are set to 0 in the output array. But 0 falls
> into the valid range for good values (0 to TOP)!

> Because it is not possible to set NANs to a value outside the valid
> range (greater than TOP), it is not possible to distinguish missing from
> valid data.

> As best I can tell, the only solution is to not use the NAN keyword and
> scale the valid data only by using WHERE to find all the valid values.
> Am I missing something obvious? (Quite possible, I admit.)

Yes, remember the NaN locations *before* you BYTSCL. Use
http://www.dfanning.com/tips/check_nan.html
to do this.

Then afterwards you can do something to the BYTSCLd array to put the NaNs
back in appropriately.

--
Edd

Report message to a moderator

[Message index]

		Re: BYTSCL and NAN keyword By: David Fanning on Tue, 02 March 2004 15:48
		Re: BYTSCL and NAN keyword By: Kenneth P. Bowman on Tue, 02 March 2004 15:18
		Re: BYTSCL and NAN keyword By: David Fanning on Tue, 02 March 2004 14:07
		Re: BYTSCL and NAN keyword By: JD Smith on Tue, 02 March 2004 13:32
		Re: BYTSCL and NAN keyword By: Craig Markwardt on Tue, 02 March 2004 09:39
		Re: BYTSCL and NAN keyword By: David Fanning on Tue, 02 March 2004 09:45
		Re: BYTSCL and NAN keyword By: K. Bowman on Tue, 02 March 2004 09:26
		Re: BYTSCL and NAN keyword By: David Fanning on Tue, 02 March 2004 09:18
		Re: BYTSCL and NAN keyword By: Edd Edmondson on Tue, 02 March 2004 09:13
		Re: BYTSCL and NAN keyword By: K. Bowman on Wed, 03 March 2004 07:26
		Re: BYTSCL and NAN keyword By: Kenneth P. Bowman on Tue, 02 March 2004 17:44

Previous Topic:	Re: 2D-fit
Next Topic:	FastDL: An MPI interface for IDL

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Sat Nov 29 00:47:47 PST 2025

Total time taken to generate the page: 1.28186 seconds