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Re: Comparing 2 arrays [message #55656 is a reply to message #55564]

Tue, 28 August 2007 11:56

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

Paul van Delst writes:

> I think you should also pass a scaling factor, ala,
>
> FUNCTION FLTARRAYS_EQUAL, array_1, array_2, ULP=ulp
> ....
> IF ( N_ELEMENTS(ulp) EQ 0 ) THEN ulp=1.0
> ....
> NUMBER = (array_1 > array_2) * epsilon * ulp
> ....
> END
>
> Also, there needs to be differentiation for singel and double precision so you can
> determine epsilon correctly and set ulp to a suitable default (1.0 or 1.0d0).

I usually save these extra touches for programs I add to
the Coyote Library and document heavily, not for ones I
throw away into the Tip Examples pile. But I have a feeling
this one is destined for the Library anyway.

I've seen you use ULP as a variable name before.
Is this something like VEGEMITE? Or does it actually
mean something to you? I'd probably call it FUDGE
if I was making up the name myself. :-)

Can double precision *possibly* make a difference in this
program in practice?

Cheers,

David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")

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[Message index]

		Comparing 2 arrays By: teich on Sat, 25 August 2007 21:18
		Re: Comparing 2 arrays By: ph le sager on Wed, 29 August 2007 10:32
		Re: Comparing 2 arrays By: David Fanning on Wed, 29 August 2007 06:17
		Re: Comparing 2 arrays By: Carsten Lechte on Wed, 29 August 2007 03:31
		Re: Comparing 2 arrays By: Allan Whiteford on Wed, 29 August 2007 01:04
		Re: Comparing 2 arrays By: James Kuyper on Tue, 28 August 2007 13:02
		Re: Comparing 2 arrays By: Jean H. on Tue, 28 August 2007 12:18
		Re: Comparing 2 arrays By: Paul Van Delst[1] on Tue, 28 August 2007 12:33
		Re: Comparing 2 arrays By: David Fanning on Tue, 28 August 2007 11:56
		Re: Comparing 2 arrays By: Paul Van Delst[1] on Tue, 28 August 2007 11:43
		Re: Comparing 2 arrays By: David Fanning on Tue, 28 August 2007 09:52
		Re: Comparing 2 arrays By: Jean H. on Tue, 28 August 2007 09:20
		Re: Comparing 2 arrays By: David Fanning on Tue, 28 August 2007 09:18
		Re: Comparing 2 arrays By: Allan Whiteford on Tue, 28 August 2007 09:10

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