Conversion from categorical SpatRast loses levels

[ailich]

When converting a SpatRast that has factor levels to a raster object, the result is no longer a factor.

library(terra)
#> Warning: package 'terra' was built under R version 4.2.2
#> terra 1.7.12
library(raster)
#> Warning: package 'raster' was built under R version 4.2.2
#> Loading required package: sp
#> Warning: package 'sp' was built under R version 4.2.2

r<- rast(matrix(data=c(1,1,1,2,2,2,3,3,3), nrow=3))
levels(r)<- data.frame(ID=1:3, class= c("c1", "c2", "c3"))
is.factor(r)
#> [1] TRUE
levels(r)
#> [[1]]
#>   ID class
#> 1  1    c1
#> 2  2    c2
#> 3  3    c3

raster(r) |> is.factor()
#> [1] FALSE
raster(r) |> levels()
#> NULL

^{Created on 2023-02-21 with reprex v2.0.2}

[rhijmans]

Thanks, I now get:

library(terra)
library(raster)
r <- rast(matrix(data=c(1,1,1,2,2,2,3,3,3), nrow=3))
levels(r)<- data.frame(ID=1:3, class= c("c1", "c2", "c3"))
raster(r)

#class      : RasterLayer 
#dimensions : 3, 3, 9  (nrow, ncol, ncell)
#resolution : 1, 1  (x, y)
#extent     : 0, 3, 0, 3  (xmin, xmax, ymin, ymax)
#crs        : NA 
#source     : memory
#names      : class 
#values     : 1, 3  (min, max)
#attributes :
# ID class
#  1    c1
#  2    c2
#  3    c3