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Re: Vector comparison. [message #37064 is a reply to message #37063]

Thu, 20 November 2003 02:19

Craig Markwardt
Messages: 1869
Registered: November 1996

Senior Member

Reimar Bauer <R.Bauer@fz-juelich.de> writes:
>>
>> Alas, Reimar, none of these gives the answer of [2,3,4,6]
>> that Mr. Hunter was looking for. :-)
>>
>> Cheers,
>>
>> David
>>
>> P.S. I know we are all busy, but maybe we should make
>> it a new rule that we all have to take a deep breath and
>> a stretch, then read the question TWICE before
>> posting an answer. :-)
>>
>
> Oh, yes you are right, I missed to post the right thing. As I started
> writing I thought I give a complete answer to all related topics.
>
>
>
> IDL> A=[0,1,3,3,3,6,7,9,9]
> IDL> B=[3,7]
> IDL> print,which_indices(a,b)

OK, now it's my turn to be nit-picky. The WHICH_INDICES routine uses
a brute force loop approach which was what the original poster was
trying to avoid.

I think that getting *all* matches without loops is a rather difficult
problem. The approach that I recommended separately involves a "fast"
intersection and then a "slow" rebuilding of a duplicates list. That
falls over too if the intersection result is large, but it should
always be about as fast as the brute force approach.

Craig

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Craig B. Markwardt, Ph.D. EMAIL: craigmnet@REMOVEcow.physics.wisc.edu
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
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[Message index]

		Re: Vector comparison. By: JD Smith on Thu, 20 November 2003 11:38
		Re: Vector comparison. By: tam on Thu, 20 November 2003 10:55
		Re: Vector comparison. By: David Fanning on Thu, 20 November 2003 09:55
		Re: Vector comparison. By: Craig Markwardt on Thu, 20 November 2003 09:35
		Re: Vector comparison. By: tam on Thu, 20 November 2003 09:24
		Re: Vector comparison. By: David Fanning on Thu, 20 November 2003 08:52
		Re: Vector comparison. By: Chris[1] on Thu, 20 November 2003 08:08
		Re: Vector comparison. By: David Fanning on Thu, 20 November 2003 08:08
		Re: Vector comparison. By: R.Bauer on Thu, 20 November 2003 07:11
		Re: Vector comparison. By: tam on Thu, 20 November 2003 07:03
		Re: Vector comparison. By: hunter on Thu, 20 November 2003 06:49
		Re: Vector comparison. By: David Fanning on Thu, 20 November 2003 05:40
		Re: Vector comparison. By: R.Bauer on Thu, 20 November 2003 04:02
		Re: Vector comparison. By: Craig Markwardt on Thu, 20 November 2003 02:19
		Re: Vector comparison. By: Chris Lee on Thu, 20 November 2003 02:09
		Re: Vector comparison. By: R.Bauer on Thu, 20 November 2003 01:01
		Re: Vector comparison. By: Craig Markwardt on Thu, 20 November 2003 00:23
		Re: Vector comparison. By: David Fanning on Wed, 19 November 2003 18:05
		Re: Vector comparison. By: R.Bauer on Wed, 19 November 2003 17:50
		Re: Vector comparison. By: Craig Markwardt on Wed, 19 November 2003 15:48
		Re: Vector comparison. By: Pavel Romashkin on Wed, 19 November 2003 16:09

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