R version 4.4.0 alpha (2024-04-02 r86304 ucrt)
Copyright (C) 2024 The R Foundation for Statistical Computing
Platform: x86_64-w64-mingw32/x64

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> options(rgdal_show_exportToProj4_warnings = "none")
> if (suppressPackageStartupMessages(require(sp, quietly = TRUE))) {
+ demo(meuse)
+ # remove +init=xxx
+ meuse@proj4string = CRS(
+ "+proj=sterea +lat_0=52.1561605555556 +lon_0=5.38763888888889 +k=0.9999079 +x_0=155000 +y_0=463000 +ellps=bessel +units=m +no_defs"
+ )
+ meuse.grid@proj4string = CRS(
+ "+proj=sterea +lat_0=52.1561605555556 +lon_0=5.38763888888889 +k=0.9999079 +x_0=155000 +y_0=463000 +ellps=bessel +units=m +no_defs"
+ )
+ 
+ suppressPackageStartupMessages(library(stars))
+ (m = st_as_stars(meuse))
+ (gr = st_as_stars(meuse.grid))
+ 
+ m2 = as(m, "Spatial")
+ summary(m2)
+ gr2 = as(gr, "Spatial")
+ summary(gr2)
+ 
+ all.equal(meuse, m2, check.attributes = FALSE)
+ fullgrid(meuse.grid) = TRUE
+ all.equal(meuse.grid, gr2, check.attributes = FALSE)
+ 
+ #all.equal(meuse, m2)
+ #all.equal(meuse.grid, gr2)
+ }


	demo(meuse)
	---- ~~~~~

> require(sp)

> crs = CRS("EPSG:28992")

> data("meuse")

> coordinates(meuse) <- ~x+y

> proj4string(meuse) <- crs

> data("meuse.grid")

> coordinates(meuse.grid) <- ~x+y

> gridded(meuse.grid) <- TRUE

> proj4string(meuse.grid) <- crs

> data("meuse.riv")

> meuse.riv <- SpatialPolygons(list(Polygons(list(Polygon(meuse.riv)),"meuse.riv")))

> proj4string(meuse.riv) <- crs

> data("meuse.area")

> meuse.area = SpatialPolygons(list(Polygons(list(Polygon(meuse.area)), "area")))

> proj4string(meuse.area) <- crs
[1] TRUE
> 
> proc.time()
   user  system elapsed 
   0.98    0.17    1.11