comp.lang.idl-pvwave archive: archive » Pair Counts in an Annulus, for large data sets

Home » Public Forums » archive » Pair Counts in an Annulus, for large data sets

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: Pair Counts in an Annulus, for large data sets [message #51501 is a reply to message #51262]

Thu, 23 November 2006 19:20

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

fatcat3131@gmail.com writes:

> Right. And that makes perfect sense to me. The problem is, my "R" data
> set is relative to some fixed origin "O". And I want to measure a
> radius "Delta-R" from a data-point R(1), not from O. Then count up the
> points which lie within "Delta-R" from R(1). Then repeat, measuring
> Delta-R from R(2) this time. Then from R(N), etc...
>
> So to me, a histogram on R is counting up the points which lie a
> certain distance from the origin, no?
>
> If you are in fact interpretting the problem correctly already, then
> I'm really sorry. Just say so and I'll keep going over it until it
> "clicks"... I just thought you might be thinking I want to measure
> Delta-R from the Origin, which is not in fact the case.

Oh, I see. I didn't read the second part of your original
post carefully. Sorry.

In this case, I think you are going to need some JD Smith
slight of hand. I would start with this article and see
if you don't get part of the way there:

http//www.dfanning.com/code_tips/slowloops.html

This article describes a situation similar to yours, and
outlines a couple of possible ways of solving the problem.
With 350000 points, you will want the one that uses the
*least* amount of memory. -)

Cheers,

David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")

Report message to a moderator

[Message index]

		Pair Counts in an Annulus, for large data sets By: fatcat3131 on Fri, 10 November 2006 21:52
		Re: Pair Counts in an Annulus, for large data sets By: David Fanning on Thu, 23 November 2006 19:20
		Re: Pair Counts in an Annulus, for large data sets By: fatcat3131 on Thu, 23 November 2006 18:47
		Re: Pair Counts in an Annulus, for large data sets By: David Fanning on Thu, 23 November 2006 07:58

Previous Topic:	Re: write_png weirdness
Next Topic:	Re: 'from lon-lat to TM' source code?

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Sun Oct 12 07:21:03 PDT 2025

Total time taken to generate the page: 1.99881 seconds