[R-sig-Geo] how to transform Polygons to SpatialPolygons

[Edzer Pebesma]

Or maybe just:

plot(sp.usa[3])
class(sp.usa[3])
[1] "SpatialPolygons"
attr(,"package")
[1] "sp"



On 06/22/2010 10:59 PM, Hans-Jörg Bibiko wrote:
> 
> On Jun 22, 2010, at 10:29 PM, Weidong Gu wrote:
> 
>>
>> The question is how to transform 'mainland' back into SpatialPolygons format. 
> 
> 
> Hi,
> 
> maybe try the following:
> 
> library(maps)
> library(maptools)
> usa=map('usa',plot=F,fill=T)
> IDs=sapply(strsplit(usa$names,':'), function(x) x[1])
> crs=CRS('+proj=longlat +ellps=WGS84')
> sp.usa=map2SpatialPolygons(usa,IDs=usa$names,proj4string=crs)
> 
> mainland <- list(slot(sp.usa,'polygons')[[3]])
> sp_mainland <- SpatialPolygons(mainland, proj4string=crs)
> str(sp_mainland)
> plot(sp_mainland)
> 
> Cheers,
> --Hans
> 
> 
> **********************************************************
> Hans-Joerg Bibiko
> Max Planck Institute for Evolutionary Anthropology
> Department of Linguistics
> Deutscher Platz 6     phone:   +49 (0) 341 3550 341
> D-04103 Leipzig       fax:     +49 (0) 341 3550 333
> Germany               e-mail:  bibiko[-at-]eva.mpg.de
> 
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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