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Re: SIGN function: signof(num or array of num) [message #70140 is a reply to message #70139]

Tue, 16 March 2010 07:30

H. Evans
Messages: 18
Registered: December 2009

Junior Member

On Mar 16, 2:57 pm, Carsten Lechte <c...@toppoint.de> wrote:
> F LDY Lajos wrote:
>> I think SIGNOF() should not cause an arithmetic error for finite numbers.
>
> I use the expression
>
> (x GT 0) -1* (x LT 0)
>
> to get the sign of e.g.
>
> x = [ -2e4, 5, 0, 1d/0, -1d/0, 0d/0 ]
>
> but it uses 2 comparisons and even a multiplication. Does anyone have
> a simpler/faster version? Furthermore, what should the sign of NaN be?
>
> chl

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

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[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

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