get_map: Get map data for a given geodomain

In andrew-MET/harpVis: Visualisation functions for harp.

Get map data for a given geodomain

Description

Given a specific domain, a map is returned on that domain. The function is intended to be used in conjunction with geom_geocontour and / or geom_georaster when plotting using ggplot().

Usage

get_map(dom = NULL, map = "world", polygon = TRUE, ...)

Arguments

dom	A geodomain or geofield
map	The map database from which to get the map data. The default is world. Datasets from the rnaturalearth package may also be used, but only paths will be returned.
polygon	Logical. Whether to return the data as polygons (TRUE), or paths (FALSE). The default is for polygons to be returned.
...	Not used.

Value

A data frame with columns "x", "y", and for polygon = TRUE an additional "group" column.

Examples

# Define a domain and make some data
arr <- array(dim = c(200, 200))
for (i in 1:200) {
  for (j in 1:200) {
    arr[i, j] <- sin(i / 10) + sin(j / 10)
  }
}

dom <- define_domain(10, 60, 200, 10000)
geo <- geofield(arr, domain = dom)
data <- data.frame(geo = geolist(geo))

# Use polygons
map <- get_map(geo)
ggplot() +
  geom_polygon(
    aes(x, y, group = group), map,
    fill = "seagreen", colour = "grey10"
  ) +
  geom_geocontour(aes(geofield = geo, colour = after_stat(level)), data) +
  coord_equal(expand = FALSE) +
  theme_harp_map()

# Use paths
map <- get_map(geo, polygon = FALSE)
ggplot() +
  geom_georaster(aes(geofield = geo), data) +
  geom_path(aes(x, y), map, colour = "grey30") +
  coord_equal(expand = FALSE) +
  theme_harp_map()

andrew-MET/harpVis documentation built on March 11, 2024, 9:34 a.m.