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Re: Extract Array positions for a set of Values [message #75434 is a reply to message #75427]

Wed, 09 March 2011 06:37

Jeremy Bailin
Messages: 618
Registered: April 2008

Senior Member

On Wednesday, March 9, 2011 5:48:42 AM UTC-5, Paul Magdon wrote:
> Hi,
> have a quite simple problem for which I can find a fas solution:
>
> 1.) I have an IntArray A (e.g a result from LABEL_REGION)
>
> 1 1 1 1 0 0 0
> 1 1 1 1 0 0 2
> 0 0 0 0 9 0 2
>
> 2.) I have a vector B with Integers (e.g. 1,2,9)
>
> Now I want to extract the positions of B in A and set all values in A which are included in B to let's say 99. How can I do this without a loop?
> I tested HISTOGRAM(,REVERSE_INDICES) but as B is not consecutive (e.g 1,2,3,4) I can't find a solution.
>
> Cheers Paul

I'd try remapping the values so that B is consecutive, and then use value_locate (come on, you *knew* it was coming...) to figure out if it's in B or not.

b_sorted = b[SORT(b)]
locations = WHERE(b_sorted[VALUE_LOCATE(b_sorted, a)] EQ a, nlocations)
IF nlocations GT 0 THEN a[locations]=99

-Jeremy.

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[Message index]

		Re: Extract Array positions for a set of Values By: wlandsman on Thu, 10 March 2011 06:54
		Re: Extract Array positions for a set of Values By: Jeremy Bailin on Thu, 10 March 2011 05:49
		Re: Extract Array positions for a set of Values By: Gray on Wed, 09 March 2011 13:29
		Re: Extract Array positions for a set of Values By: Jeremy Bailin on Wed, 09 March 2011 06:37
		Re: Extract Array positions for a set of Values By: wlandsman on Wed, 09 March 2011 03:08

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