comp.lang.idl-pvwave archive: archive » Re: SIGN function: signof(num or array of num)

Home » Public Forums » archive » Re: SIGN function: signof(num or array of num)

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

Re: SIGN function: signof(num or array of num) [message #70138 is a reply to message #70137]

Tue, 16 March 2010 08:35

Carsten Lechte
Messages: 124
Registered: August 2006

Senior Member

H. Evans wrote:
> Could be either + or -ve:
> IDL> print,!values.f_nan, - !values.f_nan
> NaN -NaN

Then, a totally different approach might be necessary to get
it completely right.

FINITE() tells you if you have a NaN, but since every
comparison that involves NaNs evaluates to FALSE, you cannot
find out if it's + or -NaN be equating to !VALUES.F_NAN.

One would have to extract the sign bit (assuming IEEE format,
taking into account endianness, precision etc.) and base the
calculation on that.

For my private version, I will add a term + ( FINITE( x) EQ 0)
so all NaNs are assumed positive, since the one value that
SIGNUM( NaN) should not have is 0.

I wonder in what situation one would care about the correct sign
of something that is not a number.

chl

Report message to a moderator

[Message index]

		Re: SIGN function: signof(num or array of num) By: Foldy Lajos on Tue, 16 March 2010 09:41
		Re: SIGN function: signof(num or array of num) By: Carsten Lechte on Tue, 16 March 2010 09:36
		Re: SIGN function: signof(num or array of num) By: Carsten Lechte on Tue, 16 March 2010 09:25
		Re: SIGN function: signof(num or array of num) By: Ding on Tue, 16 March 2010 09:17
		Re: SIGN function: signof(num or array of num) By: Carsten Lechte on Tue, 16 March 2010 08:46
		Re: SIGN function: signof(num or array of num) By: Ding on Tue, 16 March 2010 08:43
		Re: SIGN function: signof(num or array of num) By: Carsten Lechte on Tue, 16 March 2010 08:35
		Re: SIGN function: signof(num or array of num) By: Ding on Tue, 16 March 2010 08:32
		Re: SIGN function: signof(num or array of num) By: H. Evans on Tue, 16 March 2010 07:30

Previous Topic:	How to read data with format codes?
Next Topic:	Predefined iTool Visualization in existing iTool

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Fri Oct 10 21:59:07 PDT 2025

Total time taken to generate the page: 1.75953 seconds