Convert polygonal "sfg" to "gpc.poly"

Description

Package polyCub implements a converter from class "(MULTI)POLYGON" of package sf to "gpc.poly" of package rgeos (originally from gpclib) such that polyCub.exact.Gauss can be used with simple feature polygons.

Usage

sfg2gpc(object)

Arguments

Value

The converted polygon of class "gpc.poly". If neither package rgeos nor gpclib are available, sfg2gpc will just return the pts slot of the "gpc.poly" (no formal class) with a warning.

Note

Package rgeos (or gpclib) is required for the formal class definition of a "gpc.poly".

Author(s)

Sebastian Meyer

See Also

xylist

Examples

if (require("rgeos") && require("sf")) {
    ## use example polygons from
    example(plotpolyf, ask = FALSE)

    letterR  # a simple "xylist"
    letterR.sfg <- st_polygon(lapply(letterR, function(xy)
        rbind(cbind(xy$x, xy$y), c(xy$x[1], xy$y[1]))))
    print(letterR.sfg)
    stopifnot(identical(letterR, xylist(letterR.sfg)))
    
    ## convert sf "POLYGON" to a "gpc.poly"
    letterR.gpc_from_sfg <- sfg2gpc(letterR.sfg)
    print(letterR.gpc_from_sfg)
    letterR.xylist_from_gpc <- xylist(letterR.gpc_from_sfg) # with hole info
    stopifnot(identical(letterR, lapply(letterR.xylist_from_gpc, "[", 1:2)))
}