Am i misusing the shift() option in elide(maptools) function?
On Sun, 9 Dec 2007, zhijie zhang wrote:
Dear friends,
I used the shift() option in elide(maptools) function to shift the x/y
coordiates, but it seemed that it didn't change the coordinates.
#Programs used by me
library(sp)
library(foreign)
library(maptools)
data(meuse) #in the help page
coordinates(meuse) <- c("x", "y")
proj4string(meuse) <- CRS("+init=epsg:28992")
data(meuse.riv)
river_polygon <- Polygons(list(Polygon(meuse.riv)), ID="meuse")
rivers <- SpatialPolygons(list(river_polygon))
proj4string(rivers) <- CRS("+init=epsg:28992")
#rivers
Slot "coords":
[176,] 182003.7 337678.6
Slot "bbox":
min max
r1 178304.0 182331.5
r2 325698.5 337684.8
rivers1 <- elide(rivers, shift=c(10000,-10000)) #,shift southeast to 10000,
but it seems unchanged
#rivers1
#the coordinates were the same as that of rivers
Slot "coords":
[176,] 182003.7 337678.6
Slot "bbox":
min max
r1 178304.0 182331.5
r2 325698.5 337684.8
Q: Am i misusing the shift() option in elide(maptools) function? Where goes
wrong?
Thanks for a very clear report, this was a bug. The shift= argument worked for points but not for lines or polygons. The next release of maptools will correct this, and add rotation options kindly contributed by Don MacQueen. Roger
Thanks.
Roger Bivand Economic Geography Section, Department of Economics, Norwegian School of Economics and Business Administration, Helleveien 30, N-5045 Bergen, Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43 e-mail: Roger.Bivand at nhh.no