buffer from dismo package error

Hi everybody,

I am trying to create a buffer around several points using the function 
circles in the R package dismo. The problem arises with points that are 
close to the 180 or -180 longitude. In these cases the buffer is not a 
circle but a band that connect both sides of the map extension. Probably 
I am missing some basic option, but I am wondering if there is any way 
to avoid this issue. Below an example code and its result.

library(dismo)

library(rgdal)

xx<-cbind(c(-175.20, -106.65,-103.97,-17.76),c(-21.13,35.08,36.78,28.65))

pp<-as.data.frame(rep(1,4))

zz<-SpatialPointsDataFrame(xx,pp)

cc<-circles(zz,1000000,lonlat=TRUE)

plot(cc)


Thanks

Sergio A Estay

Ejemplo 9

Sergio A. Estay
Inst. Ciencias Ambientales y Evolutivas
Universidad Austral de Chile
Casilla 567, Valdivia, Chile
Phone: 5663-2293913
Web Pages: Department <http://icaev.cl/academicos/sergio-estay/>, 
Scholar 
<http://scholar.google.cl/citations?user=94JOMYcAAAAJ&hl=en&oi=ao>, 
Researchgate 
<https://www.researchgate.net/profile/Sergio_Estay2/?ev=hdr_xprf>


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