[R] Polygon-like interactive selection of plotted points
rkoenker at uiuc.edu
Wed Apr 26 20:39:26 CEST 2006
?in.convex.hull in the package tripack.
url: www.econ.uiuc.edu/~roger Roger Koenker
email rkoenker at uiuc.edu Department of Economics
vox: 217-333-4558 University of Illinois
fax: 217-244-6678 Champaign, IL 61820
On Apr 26, 2006, at 1:25 PM, Marc Schwartz (via MN) wrote:
> On Wed, 2006-04-26 at 18:13 +0100, Florian Nigsch wrote:
>> [Please CC me for all replies, since I am not currently subscribed to
>> the list.]
>> Hi all,
>> I have the following problem/question: Imagine you have a two-
>> dimensional plot, and you want to select a number of points, around
>> which you could draw a polygon. The points of the polygon are defined
>> by clicking in the graphics window (locator()/identify()), all points
>> inside the polygon are returned as an object.
>> Is something like this already implemented?
>> Thanks a lot in advance,
> I don't know if anyone has created a single function do to this
> it is always possible).
> However, using:
> RSiteSearch("points inside polygon")
> brings up several function hits that, if put together with the above
> interactive functions, could be used to do what you wish. That is,
> the matrix of x,y coords of the interactively selected polygon and the
> x,y coords of the underlying points set to return the points inside or
> outside the polygon boundaries.
> Just as an FYI, you might also want to look at ?chull, which is in the
> base R distribution and returns the set of points on the convex
> hull of
> the underlying point set. This is to some extent, the inverse of what
> you wish to do.
> Marc Schwartz
> R-help at stat.math.ethz.ch mailing list
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