invalid polygon #222

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1. edzer commented on Mar 15, 2023

   

   edzer

   on Mar 15, 2023

   MemberAuthor

   More actions

   Interestingly,

   library(s2)
   x = s2_geog_from_text("POLYGON ((0 0, 3 0, 3 2, 1 1, 2 1, 0 2, 0 0))", check = FALSE)
   o = s2_options(split_crossing_edges = TRUE, snap = s2_snap_precision(0))
   s2_rebuild(x, o) |> s2_is_valid()
   # [1] TRUE
   # Warning messages:
   # 1: In cpp_s2_rebuild(as_s2_geography(x), options) :
   #   NAs introduced by coercion to integer range
   # 2: In cpp_s2_rebuild(as_s2_geography(x), options) :
   #   NAs introduced by coercion to integer range

   but the warnings here seem to indicate that something went wrong, as x didn't change:

   library(sf)
   # Linking to GEOS 3.11.1, GDAL 3.6.2, PROJ 9.1.1; sf_use_s2() is TRUE
   s2_rebuild(x, o) |> st_as_sfc() -> y
   # Warning messages:
   # 1: In cpp_s2_rebuild(as_s2_geography(x), options) :
   #   NAs introduced by coercion to integer range
   # 2: In cpp_s2_rebuild(as_s2_geography(x), options) :
   #   NAs introduced by coercion to integer range
   y[[1]]
   # POLYGON ((0 0, 3 0, 3 2, 2 1, 1 1, 0 2, 0 0))
2. paleolimbot commented on Mar 30, 2023

   

   paleolimbot

   on Mar 30, 2023

   Collaborator

   More actions

   First, the warning is coming from s2_snap_precision(0) (i.e., log10(0)). Did you mean s2_snap_distance(0)?

   Maybe a unary union is needed to fix this one?

   library(s2)
   
   x = s2_geog_from_text("POLYGON ((0 0, 3 0, 3 2, 1 1, 2 1, 0 2, 0 0))", check = FALSE)
   o = s2_options(split_crossing_edges = TRUE)
   x |> 
     s2_is_valid()
   #> [1] FALSE
   
   x |> 
     s2_rebuild(o) |> 
     s2_is_valid()
   #> [1] FALSE
   
   x |> 
   s2_rebuild(o) |> 
     s2_union() |> 
     s2_is_valid()
   #> [1] TRUE

   ^{Created on 2023-03-30 with reprex v2.0.2}