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Re: the fastest way to find number of points in sphere(radius r) [message #46421 is a reply to message #46420]

Tue, 22 November 2005 00:31

Peter Clinch
Messages: 98
Registered: April 1996

Member

PYJ wrote:
to use a loop because I have a lot of positions of centers of
> spheres that I should examine.
> I want to find the # of points inside each sphere.
> Now, I use a where function in order to find points inside the cube,
> then I compute distances of all. Next, I use where function again to
> examine # of distances less than radius of sphere.
> I think it is fairly slow when large data is considered.
>
> Is there any faster way?
> The fastest way to find the number of points in sphere(radius r)

If you have the radius R in terms of voxels then the number of voxels in
the sphere will be 4/3 Pi R^3, surely? Seems so simple I suspect that
my not having had a coffee yet has caused me to miss something obvious...

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net p.j.clinch@dundee.ac.uk http://www.dundee.ac.uk/~pjclinch/

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[Message index]

		Re: the fastest way to find number of points in sphere(radius r) By: Xavier Llobet on Tue, 22 November 2005 11:16
		Re: the fastest way to find number of points in sphere(radius r) By: MarioIncandenza on Tue, 22 November 2005 10:18
		Re: the fastest way to find number of points in sphere(radius r) By: Haje Korth on Tue, 22 November 2005 08:53
		Re: the fastest way to find number of points in sphere(radius r) By: Xavier Llobet on Tue, 22 November 2005 08:01
		Re: the fastest way to find number of points in sphere(radius r) By: Xavier Llobet on Tue, 22 November 2005 07:29
		Re: the fastest way to find number of points in sphere(radius r) By: btt on Tue, 22 November 2005 06:00
		Re: the fastest way to find number of points in sphere(radius r) By: snfinder@naver.com on Tue, 22 November 2005 05:14
		Re: the fastest way to find number of points in sphere(radius r) By: Xavier Llobet on Tue, 22 November 2005 04:16
		Re: the fastest way to find number of points in sphere(radius r) By: Xavier Llobet on Tue, 22 November 2005 04:02
		Re: the fastest way to find number of points in sphere(radius r) By: snfinder@naver.com on Tue, 22 November 2005 03:33
		Re: the fastest way to find number of points in sphere(radius r) By: Peter Clinch on Tue, 22 November 2005 01:13
		Re: the fastest way to find number of points in sphere(radius r) By: snfinder@naver.com on Tue, 22 November 2005 01:06
		Re: the fastest way to find number of points in sphere(radius r) By: Peter Clinch on Tue, 22 November 2005 00:31
		Re: the fastest way to find number of points in sphere(radius r) By: snfinder@naver.com on Tue, 22 November 2005 22:23

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