[R-sig-Geo] RES: Defining Holes Inside a Polygon

[Rodrigo Aluizio]

Very sorry about the attached file, I'm not used to mailing lists, won't
happen again.
Well, I've already tried the checkPolygonsHoles function as specified in a
book of Yours, and even then nothing changes in the final Shapefiles, all
the polygons remain with FALSE "hole" slots.

Below are the code and sessionInfo(). 

# Required Packages
library(rgdal)
library(RODBC)
library(maptools)
gpclibPermit()

#Loading Data
Data<-odbcConnectExcel2007('Sub-Provincias-Forams-Dados.xlsx',readOnly=T)
PCdata<-sqlFetch(Data,'PC',rownames='ID')
odbcCloseAll()

# Loading Lines
PC<-MapGen2SL('PCForams.dat',proj4string=CRS('+proj=longlat +ellps=WGS84'))

# Verifing closed Lines
PCP<-sapply(slot(PC,'lines'),function (x) {
  crds<-slot(slot(x,'Lines')[[1]],'coords')
  identical(crds[1,],crds[nrow(crds),])
})

# Preparing the Poligons
PCP2<-PC[PCP==T]
lista_de_pols<-slot(PCP2,'lines')
PCSP<-SpatialPolygons(lapply(lista_de_pols, function(x) {
  Polygons(list(Polygon(slot(slot(x,'Lines')[[1]],
  'coords'))),ID=slot(x,'ID'))
}),proj4string=CRS('+proj=longlat +ellps=WGS84'))

# Defining the Holes
pls_out<-lapply(slot(PCSP,"polygons"),checkPolygonsHoles)
PCSPH<-SpatialPolygons(pls_out,proj4string=CRS('+proj=longlat
+ellps=WGS84'))
PCSPDF<-SpatialPolygonsDataFrame(PCSPH,PCdata)
writeOGR(PCSPDF,dsn='.',layer='PCForams',driver='ESRI Shapefile')

# Session Info
R version 2.12.0 (2010-10-15)
Platform: x86_64-pc-mingw32/x64 (64-bit)

locale:
[1] LC_COLLATE=Portuguese_Brazil.1252 
[2] LC_CTYPE=Portuguese_Brazil.1252   
[3] LC_MONETARY=Portuguese_Brazil.1252
[4] LC_NUMERIC=C                      
[5] LC_TIME=Portuguese_Brazil.1252    

attached base packages:
[1] grDevices datasets  splines   graphics  stats    
[6] tcltk     utils     methods   base     

other attached packages:
 [1] gpclib_1.5-1    maptools_0.7-38 lattice_0.19-13
 [4] foreign_0.8-41  RODBC_1.3-2     rgdal_0.6-28   
 [7] sp_0.9-72       svSocket_0.9-50 TinnR_1.0.3    
[10] R2HTML_2.2      Hmisc_3.8-3     survival_2.35-8

loaded via a namespace (and not attached):
[1] cluster_1.13.1 grid_2.12.0    svMisc_0.9-60 
[4] tools_2.12.0

Thanks.
Rodrigo.

-----Mensagem original-----
De: Roger Bivand [mailto:Roger.Bivand at nhh.no] 
Enviada em: sexta-feira, 5 de novembro de 2010 08:01
Para: Rodrigo Aluizio
Cc: R Help
Assunto: Re: [R-sig-Geo] Defining Holes Inside a Polygon

On Fri, 5 Nov 2010, Rodrigo Aluizio wrote:

> Hi List.
>
> I?m trying to solve an issue here, but it?s getting tricky.
>
> I have an MapGen .dat file (attached) that contains about 39 closed lines.
> Three of them (the largest ones) will be my main polygons and the rest 
> of them must become holes inside one of the three major areas. I?m 
> able to transform all the closed lines into SpatialPolygons and even 
> create shapefiles with them, but how can I modify the ?hole? slot of 
> the smaller polygons so I can keep them transparent when overlaying 
> another map (those holes will overlay islands of a raster image)?
>

Next time avoid sending 200K to over 1700 people, please, we have a planet
to protect! Put any desired attachments on a website and provide a link.

You should also have provided the code (in your message) to get from:

library(maptools)
l1 <- MapGen2SL("PCForams.dat")

to your problem - as those choices may be the cause of the problem; you have
not provided the output of sessionInfo() either. Once things are lined up,
you should - if you may - say:

gpclibPermit() # very restrictive license pls_out <- lapply(slot(SpPols0,
"polygons"), checkPolygonsHoles)
SpPols1 <- SpatialPolygons(pls_out)

Or if you can install rgeos from source on R-Forge, equivalently:

library(rgeos)
SpPols1 <- createSPComment(SpPols0)

Hope this helps,

Roger

>
>
> Thank you for the attention and help.
>
> Regards.
>
>
>
> -------------------------------------------------------------------
>
> MSc.  <mailto:r.aluizio at gmail.com> Rodrigo Aluizio
>
> Centro de Estudos do Mar/UFPR
> Laboratório de Foraminíferos e Micropaleontologia Ambiental Avenida 
> Beira Mar s/n - CEP 83255-971 Pontal do Paraná - PR - Brazil
>
>
>
>

--
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen, Norway.
voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no