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Message from discussion Simple question in IDL, looking for solution, thank you
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Heinz Stege  
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 More options Oct 23 2012, 6:20 pm
Newsgroups: comp.lang.idl-pvwave
From: Heinz Stege <public.215....@arcor.de>
Date: Wed, 24 Oct 2012 00:21:26 +0200
Local: Tues, Oct 23 2012 6:21 pm
Subject: Re: Simple question in IDL, looking for solution, thank you
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On Tue, 23 Oct 2012 15:57:20 -0400, Jeremy Bailin wrote:
>A couple of notes:

>JBIU has a weighted histogram function:
>http://astroconst.org/jbiu/jbiu-doc/math/histogram_weight.html

This is really great. I have learned something new again. Thank you,
Jeremy.

For the documentation: Jeremy's way of "chunk indexing" goes the
following way:

h=histogram(arr,min=0,reverse_indices=ri)
sum=lonarr(size(h,/dimensions))
for i=0l,n_elements(h)-1 do $
   if h[i] gt 0 then sum[i]=total(bcg[ri[ri[i]:ri[i+1]-1]],/integer)
print,sum[1:*]

Small code, very fast, and low memory consumption. This is perfect.

Cheers, Heinz

>Regarding reverse_indices using lots of memory on sparse histograms: use
>VALUE_LOCATE!
>http://www.idlcoyote.com/code_tips/valuelocate.html

>-Jeremy.


 
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