[R-sig-Geo] plot extent and/or convert extent to SpatialPolygons

[Manuel Schneider]

Agustin Lobo <alobolistas <at> gmail.com> writes:

> 
> Is it possible to plot an extent object (i.e. on top of a raster like
> it would be done for a polygon with add=TRUE)
> Or can I just convert the extent object to SpatialPolygons?
> 
> Thanks
> Agus
> 

Try

bbox2square <- function(bb)
{	
	coord.mat <- data.frame(x=rep(bb[1,],each=2),y=c(bb[2,],bb[2,2:1]))
	coord.mat <- rbind(coord.mat, coord.mat[1,])
	sq <- SpatialPolygons(list(Polygons(list(Polygon(coord.mat)), ID = 1)))
	return(as(sq, "SpatialPolygonsDataFrame"))
}

where bb <- bbox(obj)