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Re: Simple question in IDL, looking for solution, thank you [message #81762 is a reply to message #81759]

Mon, 22 October 2012 11:10

Jeremy Bailin
Messages: 618
Registered: April 2008

Senior Member

On 10/22/12 7:55 AM, Heinz Stege wrote:
> Hi Danxia,
>
> you didn't ask for a solution without a loop. So here is my simple
> answer:
>
> arr=[5,2,3,1,8,3,1,2,3]
> bcg=[1,2,3,2,1,4,2,3,5]
> sum=intarr(max(arr)+1)
> for i=0,n_elements(bcg)-1 do sum[arr[i]]+=bcg[i]
> print,sum[1:*]
>
> Cheers, Heinz
>

And of course, if you need a very efficient implementation of this (i.e.
if your arrays have millions of elements), then read the "chunk
indexing" section of JD's HISTOGRAM tutorial
http://www.idlcoyote.com/tips/histogram_tutorial.html (you HAVE read
JD's HISTOGRAM tutorial, right???)

-Jeremy.

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[Message index]

		Re: Simple question in IDL, looking for solution, thank you By: Danxia on Mon, 22 October 2012 14:37
		Re: Simple question in IDL, looking for solution, thank you By: Danxia on Mon, 22 October 2012 14:36
		Re: Simple question in IDL, looking for solution, thank you By: Jeremy Bailin on Mon, 22 October 2012 11:10
		Re: Simple question in IDL, looking for solution, thank you By: Heinz Stege on Mon, 22 October 2012 04:55
		Re: Simple question in IDL, looking for solution, thank you By: Heinz Stege on Tue, 23 October 2012 11:07

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