[R-sig-Geo] inverse overlay combination A and (not B) of polygon and SpatialPixelDataFrame

[Edzer Pebesma]

On 02/17/2011 05:07 PM, Axel Hille wrote:
> Dear OSGEO list members,

Please take a look at www.osgeo.org to find out what osgeo means.

> I have installed R-10.1 on windows XP. My problem:

The current version is 2.12.1

> I have a polygon (the border of the Zuiderzee (=IJmeer?!) in the 

Zuiderzee is the historic name of the sea that is now IJsselmeer before
the Afsluitdijk was built (zee = "sea", becoming meer = "lake"), + the
areas that have been reclaimed since and used to be sea (Flevopolders,
Noordoostpolder).

> Netherlands) and a SpatialPixelsDataFrame, containing genetic similarities 
> among watersnakes across geography, bound to the convex hull curve of the 
> sampling coordinates, around the Zuidersee). What I want, is to cut off the 
> spatial grid by the edges of the Zuiderzee.
> What I so far only got by trying the overlay function is:
> ###
> zuiderzee_union # the polygon of the Zuiderzee
> rinsl.SPix.clus.clip # the SpatialPixelDataFrame
> sel=!is.na(overlay(rinsl.SPix.clus.clip, zuiderzee_union))
> ###Â  AÂ  %over%Â  B
> rinsl.SPix.clus.union.clip <- rinsl.SPix.clus.clip[sel,]
> ##
> This operation cuts out the area, which lies in the Zuiderzee - but I just 
> need the inverse (I assume acc. to the A and (not B) boolean opeation),  
> the area which is outside the Zuiderzee.

Have you tried:

rinsl.SPix.clus.union.clip <- rinsl.SPix.clus.clip[!sel,]

> 
> Any help is much apprecited!
> Many Thanks in advance!
> 
> 
> ########################################################################
> Axel Hille (Dr. rer. nat.)
> population genetic and geography
> D-33605 Bielefeld
> ########################################################################
>         
> 
> 
> 
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-- 
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.pebesma at wwu.de