On Sat, 14 Feb 2004, Patrick Giraudoux wrote:
> Dear all,
>
> I would like to generate a circles of various diameters centered on a
> point in such a way each circle could be considered as a polygon and
> used further as such eg with the library splancs. The aim is to sweep
> each point on a grid or a "random" field of points and select
other
> points wich are included in the circle (eg inout), for neighbourhood
> analysis.
>
> I wonder if such a function has been implemented in a package? (I did
> not find anything in the archives).
>
Making a circular polygon and then using inout() feels like overkill. If
you need to stay in splancs, you could just wrap .C("pythag", ...) up
in a
function comparing the returned distance with the circle radius, having
given it the locations of the two points.
However, I think dnearneigh() in spdep will do what you need, which
returns a list of integer vectors giving the point id numbers for
neighbours satisfying the distance criteria.
Roger
> Thanks for any hint.
>
> Best regards,
>
> Patrick Giraudoux
>
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--
Roger Bivand
Econonic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Breiviksveien 40, N-5045 Bergen,
Norway, voice: +47-55959355, fax: +47-55959393; Roger.Bivand at nhh.no