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Re: SIGN function: signof(num or array of num) [message #70139 is a reply to message #70138]

Tue, 16 March 2010 08:32

Ding
Messages: 20
Registered: March 2008

Junior Member

On Mar 16, 1:31 pm, FÖLDY Lajos <fo...@rmki.kfki.hu> wrote:
> On Tue, 16 Mar 2010, Ding wrote:
>> Dear IDL users,
>
>> I cannot find the SIGN function in IDL procedures, but one in
>> Solarsoft ssw/maths/ SIGN which occupy the name, but different
>> purpose( sign(a)*b). so I wrote the SIGNOF() function which is to get
>> the sign of a number or array,
>
>> Hopefully I am not repeating someone' work! you are welcome to
>> comments!
>
>> return, fix(abs(input)/input)
>
> IDL> input=0 & help, fix(abs(input)/input)
> <Expression> INT = 0
> % Program caused arithmetic error: Integer divide by 0
>
> I think SIGNOF() should not cause an arithmetic error for finite numbers.
>
> regards,
> lajos

This is expected in my algorithm, as the sign of 0 is considered to be
0. although there is an error in the IDL language, however 0/0=0, is
still true. the power of this in array calculation

IDL> a=[[1,0][-1,0]]
IDL> print,signof(a)
1 0
-1 0

Ding Yuan

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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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