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.pebe...@wwu.de
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