[R-sig-Geo] rgeos::gBuffer() fails when passed a SpatialPolygonsDataFrame containing a single multi-part @Polygons object.

[Josh O'Brien]

Hello,

Not sure if this would be considered a bug, but it did recently bite
me (and might bite others using gBuffer(..., byid=TRUE)
programatically).


    library(sp)
    library(rgdal)
    library(rgeos)

    ## Example SpatialPolygonsDataFrame
    x <- readOGR(system.file("etc/shapes", package="spdep"), "sids")[c(89,28),]
    plot(x, col=c('dodgerblue', 'wheat'))

    ## Works fine on object with multiple @Polygons in @polygons, even
    ## if one of the @Polygons is multi-part
    gBuffer(x, width=0.01, byid=TRUE)

    ## Works with a single single-part @Polygons object in @polygons
    gBuffer(x[1,], width=0.01, byid=TRUE)

    ## Fails with a single _multi-part_ @Polygons object in @polygons
    gBuffer(x[2,], width=0.01, byid=TRUE)


Thanks (and please let me know an rgeos-specific note like this would
be better posted elsewhere),

Josh O'Brien