Write categorical RasterStack to disk with levels/attributes - r

Question

I have a rasterStack (or RasterBrick) with categorical layers. When I write it to disk, and then load it again, I lose the attributes (e.g. the levels associated to my layers).
I would like to be able to save the attributes of the layers in my .grd file. Is it possible ?
MWE:
library(raster)
list_r=list()
for(i in 1:3){
r=raster(ncol=10, nrow=10, xmx=-80, xmn=-150, ymn=20, ymx=60)
values(r) <- sample(1:5,size = ncell(r),replace = T)
r <- ratify(r)
rat <- levels(r)[[1]]
rat$name <- c('A', 'B', 'C','D','E')
levels(r) <- rat
list_r[[i]]=r
}
final_r=stack(list_r)
#The levels are included in the rasterStack
levels(final_r)
writeRaster(final_r,filename = "save.grd")
loaded_final_r=stack("save.grd")
#No levels remaining after loading
levels(loaded_final_r)

Answer 1

That is not working, but you can save them for a single layer like this
x <- writeRaster(final_r[[1]],filename = "save.grd", overwrite=T)
x
#class : RasterLayer
#dimensions : 10, 10, 100 (nrow, ncol, ncell)
#resolution : 7, 4 (x, y)
#extent : -150, -80, 20, 60 (xmin, xmax, ymin, ymax)
#crs : +proj=longlat +datum=WGS84 +no_defs
#source : save.grd
#names : layer.1
#values : 1, 5 (min, max)
#attributes :
# ID name
# 1 A
# 2 B
# 3 C
# 4 D
# 5 E