ggmapcn

ggmapcn is a ggplot2 extension package for visualizing maps of China and the world with customizable projections and cartographic styling.

Because CRAN imposes strict size limits on package data, certain large geospatial datasets used by ggmapcn cannot be bundled directly. These datasets are stored externally and retrieved automatically using check_geodata(). All high-level functions—such as geom_mapcn() and geom_world()—internally call check_geodata() to ensure that required data files exist locally.

If the network is unavailable or remote mirrors cannot be reached, check_geodata() fails gracefully by returning NA paths. This behavior is fully compliant with CRAN’s policy for optional network resources.

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Installation

Install the development version from GitHub:

# install.packages("devtools")
devtools::install_github("Rimagination/ggmapcn", force = TRUE)

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Data Management with check_geodata()

Several datasets—such as world_countries.rda, China_sheng.rda, and gebco_2024_China.tif—are hosted externally.
check_geodata() automatically:

• searches for existing files in:
  • user-specified local_dirs
  • the package extdata directory
  • the per-user cache directory via tools::R_user_dir("ggmapcn", "data")
• downloads missing files from mirrors (jsDelivr and GitHub)
• verifies checksums when available
• retries on failure and supports resume capability
• returns NA instead of errors when mirrors cannot be reached

To check and retrieve all files:

check_geodata()

To retrieve explicitly the datasets used by geom_world():

check_geodata(c(
  "world_countries.rda",
  "world_coastlines.rda",
  "world_boundaries.rda"
))

If your network cannot access cdn.jsdelivr.net or raw.githubusercontent.com, you may manually download the files and place them in a directory passed to local_dirs.

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Usage Examples

1. Basic Map of China

library(ggplot2)
library(ggmapcn)

ggplot() +
  geom_mapcn() +
  geom_boundary_cn() +
  theme_minimal()

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2. Custom Projection (Albers)

ggplot() +
  geom_mapcn(
    crs = "+proj=aea +lat_1=25 +lat_2=47 +lat_0=0 +lon_0=105 +datum=WGS84",
    fill = "white",
    color = "black",
    size = 0.7
  ) +
  geom_boundary_cn() +
  theme_bw()

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3. Adding Mainland Borders and Coastlines

ggplot() +
  geom_mapcn(fill = NA) +
  geom_boundary_cn(
    mainland_color = "black",
    mainland_size = 0.5,
    coastline_color = "skyblue",
    coastline_size = 0.5
  ) +
  theme_bw()

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4. Buffer Zones

ggplot() +
  geom_buffer_cn(mainland_dist = 40000) +
  geom_buffer_cn(mainland_dist = 20000, fill = "#BBB3D8") +
  geom_mapcn(fill = "white") +
  geom_boundary_cn() +
  theme_bw()
#> Warning: attribute variables are assumed to be spatially constant throughout
#> all geometries
#> Warning: attribute variables are assumed to be spatially constant throughout
#> all geometries

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5. World Map (WGS84)

ggplot() +
  geom_world(show_ocean = FALSE) +
  theme_bw()

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Data Sources

China administrative boundaries

Provided by Tianditu
https://cloudcenter.tianditu.gov.cn/administrativeDivision/

Province-, prefecture-, and county-level boundaries are preprocessed and simplified for efficient rendering in ggplot2.

Global administrative boundaries

The global dataset (countries, coastlines, and political boundaries) is curated and maintained by the package authors. It is optimized for consistent cartographic outputs across world projections and supports antimeridian splitting.

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Learn More

See the Articles for tutorials on:

• global projections and antimeridian handling
• elevation and raster overlays
• vegetation and environmental data
• styling world and China maps
• regional vs. global map workflows

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