comp.lang.idl-pvwave archive: archive » Re: Filtering out NaNs

Home » Public Forums » archive » Re: Filtering out NaNs

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

Re: Filtering out NaNs [message #8510 is a reply to message #8502]

Thu, 20 March 1997 00:00

bowman
Messages: 121
Registered: September 1991

Senior Member

In article <5grgr3$7ih@News.Dal.Ca>, sritcey@is.dal.ca (Stephen Ritcey) wrote:

> while Ken Bowman suggested using the FINITE function:
>
> b= a (finite (a)) ; exclude .... what? (see below)
>

>
> What exactly does FINITE do on IDL?

You may also find the new IDL system variable, !VALUES handy.

IDL> HELP, !VALUES, /STRUCT
** Structure !VALUES, 4 tags, length=24:
F_INFINITY FLOAT INF
F_NAN FLOAT NaNQ
D_INFINITY DOUBLE INF
D_NAN DOUBLE NaNQ

IDL> x = FINDGEN(3)
IDL> x(1) = !VALUES.F_NAN
IDL> x(2) = !VALUES.F_INFINITY
IDL> PRINT, x
0.00000 NaNQ INF
IDL> PRINT, WHERE(x EQ !VALUES.F_NAN)
-1
IDL> PRINT, WHERE(x EQ !VALUES.F_INFINITY)
2
IDL> PRINT, FINITE(x)
1 0 0

So in IDL, at least, infinity is equal to infinity, but NAN is not equal
to NAN. FINITE returns false for both infinity and NAN with no error
message.

BTW, this is on:
IDL. Version 4.0.1a (OSF alpha).
Your mileage may vary by platform.

One last tidbit

IDL> x(2) = -!VALUES.F_INFINITY
IDL> print, x
0.00000 NaNQ -INF
IDL> PRINT, WHERE(x EQ !VALUES.F_INFINITY)
-1

So you can test for + or - infinity.

Ken Bowman

--
Kenneth P. Bowman, Assoc. Prof. 409-862-4060
Department of Meteorology 409-862-4132 fax
Texas A&M University bowman@csrp.tamu.edu
College Station, TX 77843-3150
Satellite ozone movies on CD-ROM --> http://www.lenticular.com/

Report message to a moderator

[Message index]

		Re: Filtering out NaNs By: Dale Bailey on Thu, 20 March 1997 00:00
		Re: Filtering out NaNs By: thompson on Thu, 20 March 1997 00:00
		Re: Filtering out NaNs By: peter on Thu, 20 March 1997 00:00
		Re: Filtering out NaNs By: bowman on Thu, 20 March 1997 00:00
		Re: Filtering out NaNs By: f055 on Thu, 20 March 1997 00:00
		Re: Filtering out NaNs By: sritcey on Thu, 20 March 1997 00:00
		Re: Filtering out NaNs By: bowman on Wed, 19 March 1997 00:00
		Re: Filtering out NaNs By: davidf on Wed, 19 March 1997 00:00
		Re: Filtering out NaNs By: Tim Patterson on Wed, 19 March 1997 00:00

Previous Topic:	Time Series Analysis
Next Topic:	Re: Anything better than ANNOTATE?

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Sun Nov 30 20:59:02 PST 2025

Total time taken to generate the page: 0.96488 seconds