inst/doc/registering_maps.R

In cartographer: Turn Place Names into Map Data

## ----include = FALSE----------------------------------------------------------
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)

## ----setup--------------------------------------------------------------------
library(cartographer)

## -----------------------------------------------------------------------------
# in R/zzz.R
.onLoad <- function(libname, pkgname) {
  cartographer::register_map(
    "my_package.uk",
    data = rnaturalearth::ne_states(country = "united kingdom", returnclass = "sf"),
    feature_column = "name_en",
    outline = rnaturalearth::ne_countries(
      country = "united kingdom", returnclass = "sf", scale = "large"
    )
  )
}

## ----eval=FALSE---------------------------------------------------------------
# # Preserve the original coordinate reference system.
# crs_orig <- sf::st_crs(high_res_sf_data_frame)
# 
# # Convert to a more suitable CRS for manipulation. Note that the lat_ts argument
# # here is the "latitude of true scale", i.e. the latitude at which scale will be
# # the least distorted. Adjust this based on your data.
# crs_working <- sf::st_crs("+proj=eqc +lat_ts=34 units=m")
# 
# # Choose a resolution: features smaller than this scale will be lost.
# tolerance_m <- 1000L
# 
# low_res <- high_res_sf_data_frame |>
#   sf::st_transform(crs_working) |>
#   sf::st_simplify(dTolerance = tolerance_m) |>
#   sf::st_transform(crs_orig)
# 
# # Compare the size after reducing the resolution:
# object.size(high_res_sf_data_frame)
# object.size(low_res)

## ----eval=FALSE---------------------------------------------------------------
# new_geom <- geom |>
#   sf::st_transform(crs_working) |>
#   sf::st_union() |>
#   nngeo::st_remove_holes() |>
#   sf::st_make_valid()