I like that solution; it seems intuitive, and as this seems to be a FAQ,
I would like to copy this behaviour to sp classes, such that
obj[geom,] # in case there are attribute data in obj, or
obj[geom] # in case obj has only geometry
return the items in obj that are within the geometry of geom. This would
liberate us from selecting the non-NA indexes returned from overlay (or
in case of a grid, assign NA to everything outside).
A problem occurs when obj is pixels or a grid (or raster or im), and
geom lines or polygons, I can see two difficult cases:
- the grid cell centre does not, but part of the grid cell does overlap
with geom or cross geom,
- the grid cell touches geom, but does not overlap / cross.
Robert, how does raster deal with these two cases? Does it have fixed
behaviour, or can the user choose?
Rolf, how does spatstat deal with these two cases?
On 10/30/2010 12:23 AM, Turner Rolf wrote:
>
> ________________________________________
> From: r-sig-geo-boun...@stat.math.ethz.ch
> [r-sig-geo-boun...@stat.math.ethz.ch] On Behalf Of Peter Larson
> [pslars...@gmail.com]
> Sent: Saturday, 30 October 2010 8:28 a.m.
> To: r-sig-geo@stat.math.ethz.ch
> Subject: [R-sig-Geo] convert from spatstat to sp
>
> Hello all,
>
> Is there any way to convert from spatstat to sp?
>
> Specifically, I am looking to clip a density plot produced in spatstat
> to include only points within a polygon boundary in a shapefile. if
> there is a way to clip in spatstat, this would also be acceptable.
>
> Clipping in spatstat is done simply using [] --- let X be your density plot
> (image; object of class "im")
> and let W be an object of class owin determined by the polygonal boundary
> that you have in mind.
>
> Just do
>
> Y <- X[W]
>
> to get X clipped to the window W. To find out how to make ``a polygon
> boundary in a shapefile'' into
> a window, see the vignette on handling shapefiles in spatstat:
>
> vignette("shapefiles")
>
> cheers,
>
> Rolf Turner
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo@stat.math.ethz.ch
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
--
Edzer Pebesma
Institute for Geoinformatics (ifgi), University of Münster
Weseler Straße 253, 48151 Münster, Germany. Phone: +49 251
8333081, Fax: +49 251 8339763 http://ifgi.uni-muenster.de
http://www.52north.org/geostatistics e.pebe...@wwu.de
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