Register a new feature type

This adds a new feature type that can then be used by all the geoms in this package. If registering from another package, this should occur in the .onLoad() hook in the package.

Usage

register_map(
  feature_type,
  data,
  feature_column,
  aliases = NULL,
  outline = NULL,
  lazy = TRUE
)

Arguments

feature_type

Name of the type. If registering from within a package, the suggested format is "<package name>.<map name>" to avoid clashes between packages.

data

A simple feature data frame with the map data, or a function that returns a data frame. When lazy is TRUE, the value will not be evaluated until the data is first accessed.

feature_column

Name of the column of data that contains the feature names.

aliases

Optional named character vector or list that maps aliases to values that appear in the feature column. This allows abbreviations or alternative names to be supported.

outline

Optional sf geometry containing just the outline of the map, or a function returning such a geometry. When lazy is TRUE, the value will not be evaluated until the data is first accessed.

lazy

When TRUE, defer evaluation of data and outline until it is used.

Value

No return value; this updates the global feature registry.

Details

Registration supports delayed evaluation (lazy loading). This is particularly useful for larger datasets, so that they are not loaded into memory until they are accessed.

See also

vignette("registering_maps")

Examples

# register a map of the states of Italy from rnaturalearth using the
# Italian names, and providing an outline of the country
register_map(
  "italy",
  data = rnaturalearth::ne_states(country = "italy", returnclass = "sf"),
  feature_column = "name_it",
  outline = rnaturalearth::ne_countries(country = "italy", returnclass = "sf", scale = "large")
)