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Re: how to get index of array B data in array A [message #14603 is a reply to message #14601]

Thu, 11 March 1999 00:00

Gary Fu
Messages: 9
Registered: April 1997

Junior Member

David,

Thanks for your quick response. Is there any other methods without
using
the FOR loop, since my A and B array may have more than 250000 elements
?

Thanks.

Gary
>
> Gary Fu (gfu@seadas.gsfc.nasa.gov) writes:
>
>> Is there a simple way to get the index of the array B data in array A ?
>>
>> For example : A = [10,20,30,40,50], B = [10, 20, 33, 10, 30, 40, 9]
>> I want like to get the index array of B in A [0, 1, -1, 0, 2, 3, -1]
>
> I'm afraid you are stuck doing this in a loop because of
> the way the WHERE function compares unequally-sized arrays.
> But you can certainly do something like this:
>
> A = [10,20,30,40,50]
> B = [10, 20, 33, 10, 30, 40, 9]
> C = Indgen(N_Elements(B))
> FOR j=0, N_Elements(B)-1 do C[j] = (Where(A EQ B[j]))[0]
> Print, C
> 0 1 -1 0 2 3 -1
>
> Cheers,
>
> David

*****************************************
* Gary Fu, GSC (301) 286-7107 *
* email : "gfu@seadas.gsfc.nasa.gov" *
* NASA/Goddard Space Flight Center *
*****************************************

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[Message index]

		Re: how to get index of array B data in array A By: davidf on Thu, 11 March 1999 00:00
		Re: how to get index of array B data in array A By: Gary Fu on Thu, 11 March 1999 00:00
		Re: how to get index of array B data in array A By: davidf on Thu, 11 March 1999 00:00

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