[R-sig-Geo] Question about Polgons()

[Edzer Pebesma]

On 06/07/2012 11:04 PM, Struve,Juliane wrote:
> Dear list,
> 
> In the documentation about SpatialPolygons-class (code is given below) what does the line
> 
> Srs3 = Polygons(list(Sr3, Sr4), "s3/4") mean and why is it needed  ?

It does not mean anything, and it is not needed, but it illustrates
that, unlike Srs1 and Srs2, a Polygons object can also contain more than
one ring (hence the 's' in Polygons).

> 
> Thanks a lot in advance,
> 
> Juliane
> 
> Sr1 = Polygon(cbind(c(2,4,4,1,2),c(2,3,5,4,2)))
> Sr2 = Polygon(cbind(c(5,4,2,5),c(2,3,2,2)))
> Sr3 = Polygon(cbind(c(4,4,5,10,4),c(5,3,2,5,5)))
> Sr4 = Polygon(cbind(c(5,6,6,5,5),c(4,4,3,3,4)))
> Srs1 = Polygons(list(Sr1), "s1")
> Srs2 = Polygons(list(Sr2), "s2")
> Srs3 = Polygons(list(Sr3, Sr4), "s3/4")
> SpP = SpatialPolygons(list(Srs1,Srs2,Srs3))
> plot(SpP, col = 1:3, pbg="white")
> 
> 
> 
> Dr. Juliane Struve
> Fisheries and Aquatic Sciences
> 7922 NW 71st Street, Gainesville, FL 32653
> 352-273-3632 (tel)
> 352-392-3672 (fax)
> email: jstruve at ufl.edu<mailto:jstruve at ufl.edu>
> 
> 
> 
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> 
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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