| Re: Select values from one array that match multiple values from an other array [message #82479 is a reply to message #82218] |
Thu, 13 December 2012 10:24  |
Sir Loin Steak
Messages: 42
Registered: January 2012
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Member |
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On Thursday, December 13, 2012 4:35:28 PM UTC, David Fanning wrote:
> David Fanning writes:
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>> OK, I just added a POSITIONS keyword to SetIntersection
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>> that will return the positions in vector A where the
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>> values in vector B appear.
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>>
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>> A=[1,3,2,5,2,6,1,9]
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>> B=[1,5]
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>> C = SetIntersection(a, b, Positions=pos)
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>> Print, pos
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>> 0 6 3
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> At Bob Stockwell's suggestion (and with his code!) I
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> have added the keywords INDICES_A and INDICES_B
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> to this program to allow you to return the matching
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> indices in BOTH vectors. Note that this assumes the
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> vectors A and B contain *unique* values. In other
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> words, INDICES_A and POSITIONS are identical vectors
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> IF vector A and B contain unique values. If they
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> don't, then POSITIONS will contain ALL of the locations
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> in vector A where the match occurs.
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> You can find the updated program here:
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> http://www.idlcoyote.com/programs/setintersection.pro
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> Cheers,
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> David
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> --
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> David Fanning, Ph.D.
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> Fanning Software Consulting, Inc.
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> Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
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> Sepore ma de ni thue. ("Perhaps thou speakest truth.")
I was just about to post a question about this very topic - spooky! Would it also be possible to amend the SetDifference code so it also records positions, as I would like to know which elements of one array have no match in a different array.
Many thanks
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