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Re: Select values from one array that match multiple values from an other array [message #82212]

Fri, 30 November 2012 08:32

Craig Markwardt
Messages: 1869
Registered: November 1996

Senior Member

Y

On Friday, November 30, 2012 10:15:28 AM UTC-5, PMagdon wrote:
> Dear all,
>
> I tried to use WHERE for multiple comparisons of two arrays.
>
> Here is a minimal example:
> 1.) Two arrays
> A=[1,3,2,5,2,6,1,9]
> B=[1,5]
> 2.) I need to extract all positions of A where any of the values from B occur in A. So that C should look like this:
> C=[0,3,6]

You can also try MATCH2 from the IDL astronomy library.
http://idlastro.gsfc.nasa.gov/ftp/pro/misc/match2.pro
This routine tells you which item in B matches A as well.
For example,

match2, a, b, suba
;; ---> [0L,-1L,-1L,1L,-1L,-1L,0L,-1L]
;; 0 1 2 3 4 5 6 7

indicates that A[0] matches B[0], A[3] matches B[1], and A[6] matches B[0]. You didn't actually ask for this level of information, but you can get what you want by using WHERE(SUBA GE 0).

Craig

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[Message index]

		Re: Select values from one array that match multiple values from an other array By: Craig Markwardt on Fri, 30 November 2012 08:32
		Re: Select values from one array that match multiple values from an other array By: David Fanning on Fri, 30 November 2012 08:22
		Re: Select values from one array that match multiple values from an other array By: PMagdon on Fri, 30 November 2012 08:13
		Re: Select values from one array that match multiple values from an other array By: David Fanning on Fri, 30 November 2012 07:57
		Re: Select values from one array that match multiple values from an other array By: David Fanning on Fri, 30 November 2012 07:36
		Re: Select values from one array that match multiple values from an other array By: David Fanning on Fri, 30 November 2012 07:31
		Re: Select values from one array that match multiple values from an other array By: David Fanning on Thu, 13 December 2012 08:35

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