R/boundingbox.R

In jae0/aegis: Assessment of ecosystems using GIS

    boundingbox = function( x, y, buffer=0, returnvalue="sf", proj4string=projection_proj4string("lonlat_wgs84") ) {

      xr = range(x, na.rm=TRUE)
      yr = range(y, na.rm=TRUE)

      if ( buffer != 0 ) {
        xv = diff(xr) * buffer
        yv = diff(yr) * buffer
        xr[1] = xr[1] - xv
        xr[2] = xr[2] + xv
        yr[1] = yr[1] - yv
        yr[2] = yr[2] + yv
      }
      out = rbind(
        c( xr[1], yr[2] ),
        c( xr[2], yr[2] ),
        c( xr[2], yr[1] ),
        c( xr[1], yr[1] ),
        c( xr[1], yr[2] )
      )

      if (returnvalue=="sp") out = SpatialPolygons( list(Polygons(list(Polygon(out)),"bbox")), proj4string=CRS(proj4string)  )
      if (returnvalue=="sf") {
        out = (
          st_sfc( st_multipoint( out ), crs=st_crs(proj4string) )
          %>% st_union()
          %>% st_cast("POLYGON" )
          %>% st_make_valid()
        )
      }

      return(out)
    }