R/bbox2polygon.R

In hansoleorka/myR: Collection of r functions for hansoleorka

#' Create polygon from bounding box
#' 
#' Create a square polygon from a the bounding box of input geometry. 
#' 
#' @param obj spatial object or object with existing bbox method.
#' @param ID unique identifier of polygon, defaults to name of first column
#' @return a object of class SpatialPolygons
#' @details Check function...  
#' @author Hans Ole {\O}rka \email{hans.ole.orka@@gmail.org}
bbox2polygon <- function(obj,ID=names(obj)[1]){
  if(class(obj) == "matrix") {
	bb <- obj
     crs <- NA 
  }	
  if(attr(class(obj),"package") == "sp") {
	bb <- bbox(obj)
	crs <- CRS(proj4string(obj))
  }
  x <- c(bb[1,1],bb[1,2],bb[1,2],bb[1,1],bb[1,1])
  y <- c(bb[2,1],bb[2,1],bb[2,2],bb[2,2],bb[2,1]) 
  #SpatialPolygons(list(Polygons(list(Polygon(cbind(x,y))),ID=ID)),proj4string=crs)
  Srs <- Polygons(list(Polygon(cbind(x,y))),ID=ID)
  return(Srs)
}