
R version 4.3.1 (2023-06-16) -- "Beagle Scouts"
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Platform: x86_64-pc-linux-gnu (64-bit)

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> options("rgdal_show_exportToProj4_warnings"="none")
> library(sp)
> g = SpatialGrid(GridTopology(c(5,5), c(10,10), c(3,3)))
> p = as(g, "SpatialPolygons")
> p$z = c(1,0,1,0,1,0,1,0,1)
> cc = coordinates(g)
> pts = cbind(c(9,21,21,9,9),c(9,9,21,21,9))
> sq = SpatialPolygons(list(Polygons(list(Polygon(pts)), "ID")))
> rnd2 = function(x) round(x, 2)
> 
> 
> proc.time()
   user  system elapsed 
  0.556   0.042   0.592 
