Error when generating BAUs from SpatialPolygonsDataFrame

[agila5]

Dear package authors,

I created this issue since, for some reason, I'm not able to create a BAU object using auto_BAUs() when then input data is a SpatialPolygonsDataFrame. For example:

library(sp)
library(FRK)
#> 
#> Attaching package: 'FRK'
#> The following object is masked from 'package:stats':
#> 
#>     simulate
library(sf)
#> Linking to GEOS 3.13.0, GDAL 3.10.1, PROJ 9.5.1; sf_use_s2() is TRUE

nc <- st_read(system.file("shape/nc.shp", package="sf"), quiet = TRUE)
nc <- st_transform(nc, 32119)
nc_sp <- as(nc, "Spatial")
class(nc_sp)
#> [1] "SpatialPolygonsDataFrame"
#> attr(,"package")
#> [1] "sp"

auto_BAUs(
  manifold = plane(), 
  cellsize = c(10000, 10000), 
  type = "grid", 
  data = nc_sp, 
  convex = -0.05, 
  nonconvex_hull = FALSE
) -> tmp
#> Error:
#> ! unable to find an inherited method for function 'coordnames<-' for signature 'x = "SpatialPoints", value = "NULL"'

while equivalent code with SpatialPointsDataFrame works perfectly.

nc_centroid <- nc |> st_centroid()
#> Warning: st_centroid assumes attributes are constant over geometries
nc_centroid_sp <- as(nc_centroid, "Spatial")
class(nc_centroid_sp)
#> [1] "SpatialPointsDataFrame"
#> attr(,"package")
#> [1] "sp"

auto_BAUs(
  manifold = plane(), 
  cellsize = c(10000, 10000), 
  type = "grid", 
  data = nc_centroid_sp, 
  convex = -0.05, 
  nonconvex_hull = FALSE
) -> tmp

^{Created on 2026-01-26 with reprex v2.1.1.9000}

Just to be clear, this is not a real issue since I can easily fix my real-data problem just by taking the centroids of the polygons, but I was wondering whether I was misinterpreting the docs or there is a real issue in the code. Thanks!