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Re: arrays as subscripts [message #30803 is a reply to message #30797]

Thu, 16 May 2002 21:05

mperrin+news
Messages: 81
Registered: May 2001

Member

David Fanning <david@dfanning.com> wrote:
> lyubo (lzagorch@cs.wright.edu) writes:
>
>> Suppose I have 3 arrays with the same dimensions: A, B and C.
>>
>> I have to use the non zero elements of A as index to access B, then use
>> the accessed values from B as index to access C, and finally store the
>> values from C in a new array at the previously indexed positions of B.
>>
>> Is there an effective way to do that in IDL? I can write a call to a
>> C function but I was wondering if I can do it only in IDL.
>>
>> Any examples and help would be appreciated.
>
> I'm doing this after a couple of beers, so...
>
> I = Where(A GT 0, count)
> IF count GT 0 THEN BEGIN
> bindex = b[i]
> b[i] = c[bindex]
> ENDIF

He said a new array, though, for the last one, so something like

newarr = fltarr(n_elements(B)) ; or whatever type of arr it is
I = Where(A GT 0, count)
IF count GT 0 THEN BEGIN
newarr[i] = c[b[i]]
ENDIF

I think that's what he was getting at...

- Marshall

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[Message index]

		Re: arrays as subscripts By: lyubo on Fri, 17 May 2002 13:38
		Re: arrays as subscripts By: Dick Jackson on Fri, 17 May 2002 07:52
		Re: arrays as subscripts By: David Fanning on Fri, 17 May 2002 00:54
		Re: arrays as subscripts By: mperrin+news on Thu, 16 May 2002 21:05
		Re: arrays as subscripts By: David Fanning on Thu, 16 May 2002 20:39

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