Accessible and citable maps • countryatlas

A published map should say what it shows to a reader who cannot see it, be readable with a colour-vision deficiency, and say where its numbers came from.

Alt text

Every map verb sets its alt text from the final plot (Lundgard & Satyanarayan’s levels 1 and 2):

map_alt_text(p)
#> [1] "Choropleth map of GDP per capita (constant 2015 US$) (gdp_per_capita) by country, Equal Earth projection. Coloured in 5 quantile classes from 269 to 247K. 199 of 238 countries have data. Highest: Monaco (247K), Bermuda (117K), Luxembourg (104K). Lowest: Burundi (269), Afghanistan (374), Central African Republic (390). Europe has the highest median (22.7K). 16% of countries have no data."

knitr does not ask ggplot2 for it, so set it on the chunk from a plot built in an earlier chunk, as this page does:

Choropleth map of GDP per capita (constant 2015 US$) (gdp_per_capita) by country, Equal Earth projection. Coloured in 5 quantile classes from 269 to 247K. 199 of 238 countries have data. Highest: Monaco (247K), Bermuda (117K), Luxembourg (104K). Lowest: Burundi (269), Afghanistan (374), Central African Republic (390). Europe has the highest median (22.7K). 16% of countries have no data.

Colour vision

check_palette() simulates the three common deficiencies and reports the smallest difference between adjacent classes:

check_palette(p)
#> # A tibble: 4 × 3
#>   vision       min_delta_e between                          
#>   <chr>              <dbl> <chr>                            
#> 1 normal              37.7 269 to 1.68K and 1.68K to 4.65K  
#> 2 deuteranopia        19.5 269 to 1.68K and 1.68K to 4.65K  
#> 3 protanopia          23.9 269 to 1.68K and 1.68K to 4.65K  
#> 4 tritanopia          18.2 4.65K to 10.3K and 10.3K to 30.1K

Provenance and citation

map_provenance(p)
cat(map_citation(p), sep = "\n\n")
#> World Bank WDI (2026). "GDP per capita (constant 2015 US$)." Series
#> NY.GDP.PCAP.KD; release 2026-07; accessed 2026-10-02; licence CC BY
#> 4.0.
#> 
#> Natural Earth (2024). _Natural Earth: Free vector and raster map data_.
#> Natural Earth. Version 5.1.1, 1:50m admin-0 countries; public domain,
#> <https://www.naturalearthdata.com/>.
#> 
#> Savric B, Patterson T, Jenny B (2019). "The Equal Earth map
#> projection." _International Journal of Geographical Information
#> Science_, *33*(3), 454-465. doi:10.1080/13658816.2018.1504949
#> <https://doi.org/10.1080/13658816.2018.1504949>.
#> 
#> Brewer C, Pickle L (2002). "Evaluation of methods for classifying
#> epidemiological data on choropleth maps in series." _Annals of the
#> Association of American Geographers_, *92*(4), 662-681.
#> doi:10.1111/1467-8306.00310 <https://doi.org/10.1111/1467-8306.00310>.