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Re: where, or, and loops. There has to be a better way. [message #83564 is a reply to message #83474]

Fri, 08 March 2013 15:55

Jeremy Bailin
Messages: 618
Registered: April 2008

Senior Member

On 3/8/13 5:47 PM, AB wrote:
> Please see the below example to demonstrate my problem:
>
> --------------------------------
>
>
> ; This is a large floating point array of river basins
> huc = fltarr(4800,4800)
>
> ; IDs of the basins I want to extract
> NEW = [1102,1103,1104,1105]
>
> ; Find where the basins are
> pos = where(huc eq NEW[0] or $ ; IS THIS THE ONLY WAY TO FIND THE VALUES IN THE LARGER ARRAY??
> huc eq NEW[1] or $
> huc eq NEW[2] or $
> huc eq NEW[3])
>
> ; Create new array and insert basins
> key = intarr(4800,4800)
>
> key(pos) = 1
> ---------------------------------
>
> THe issue here is, what happens when the 'NEW' variable has 300 values in it? Do I have to go through 300 iterations of:
>
> pos = where(huc eq NEW[1] or $
> ............... or $
> huc eq NEW[299])
>
>
> I hope someone has found a way around this.
>
> Thanks for any ideas you can give!!!
> Annie
>
>
>
>

I like the following paradigm for these. It assumes that new is sorted -
you'll need to pre-sort it otherwise.

pos = WHERE(new[VALUE_LOCATE(new, huc)] eq huc)

-Jeremy.

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[Message index]

		where, or, and loops. There has to be a better way. By: anniebryant@gmail.com on Fri, 08 March 2013 15:47
		Re: where, or, and loops. There has to be a better way. By: Jeremy Bailin on Fri, 08 March 2013 15:55
		Re: where, or, and loops. There has to be a better way. By: wlandsman on Fri, 08 March 2013 16:30
		Re: where, or, and loops. There has to be a better way. By: cgguido on Fri, 08 March 2013 16:22

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