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Re: Vector comparison. [message #37120 is a reply to message #37068]

Thu, 20 November 2003 00:23

Craig Markwardt
Messages: 1869
Registered: November 1996

Senior Member

David Fanning <david@dfanning.com> writes:
> 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. :-)

Heh, I am guilty of the same thing in my own reply. The original
poster's requirement of keeping duplicates is a bit harder. From my
experience, an efficient set-intersection routine is very likely going
to do a sort/unique, which removes duplicates.

If one knows that the intersection is going to be small, then a simple
post-processing loop, with a brute force search, will do the trick.

As in:
c0 = cmset_op(a, 'AND', b, /index, count=ct)
if ct EQ 0 then message, 'ERROR: No intersection found'

c = -1L
for i = 0 , n_elements(c0)-1 do begin & wh = where(a EQ a(c0(i)), ct) & $
if ct GT 0 then c = [c, wh] & end
c = c(1:*)

Craig

--
------------------------------------------------------------ --------------
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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