[R-sig-Geo] finding CRS from latitude/longitude

[alemante zd]

Dear all,

I would like to sp transform my latitude/longitude vector to by first
telling it what CRS it is. This is what I did.

F1<-data.frame(x, y)
coordinates(F1)=~x+y
SP<-SpatialPoints(F1,proj4string=CRS("+proj=longlat"))
pts = SpatialPixels(SpatialPoints(F1))
gridded(F1) = TRUE

but I keep on getting the message that CRS is wrong.
Coordinate Reference System (CRS) arguments: NA

Could you please advice me on how I can get it right?

cheers
minti