s2_simplify()

[paleolimbot]

It's possible to get some simplification using s2_options(snap_radius = <radians>), but it doesn't truly simplify in the same way that sf::st_simplify() does. Also, BigQuery ST_SIMPLIFY() is a thing, so it must be possible somewhere.

library(s2)
s2_union(
  "LINESTRING (0 0, 0 1, 0 2, 0 3, 0 4)",
  options = s2_options(snap_radius = 1.5 * pi / 180)
)
#> <s2_geography[1]>
#> [1] <LINESTRING (0 0, 0 2, 0 4)>

^{Created on 2020-06-21 by the reprex package (v0.3.0)}

Points can probably be simplified by snap + union, there is a dedicated class for simplifying polylines, but I haven't seen a polygon simplifier yet.

[edzer]

Doesn't S2Builder::set_simplify_edge_chains(true) do this? The snap radius then is the simplification parameter, as dTolerance in sf::st_simplify. We could pass this in options?

[paleolimbot]

!!!!

Very cool, definitely the way to go.

[paleolimbot]

Still working on the details, but this is looking really good in #70!

library(s2)
library(sf)
#> Linking to GEOS 3.7.2, GDAL 2.4.2, PROJ 5.2.0
st_as_sfc.s2_geography <- function(x) st_as_sfc(s2_as_binary(x))

germany <- s2_data_countries("Germany")
germany %>% st_as_sfc() %>% plot()

withr::with_par(list(mfrow = c(2, 2)), {
  s2_simplify(germany, 1e2) %>% st_as_sfc() %>% plot(main = "0.1 km")
  s2_simplify(germany, 1e3) %>% st_as_sfc() %>% plot(main = "1 km")
  s2_simplify(germany, 1e4) %>% st_as_sfc() %>% plot(main = "10 km")
  s2_simplify(germany, 1e5) %>% st_as_sfc() %>% plot(main = "100 km")
})

^{Created on 2020-07-08 by the reprex package (v0.3.0)}