Choropleth map with R
A choropleth map is a type of thematic map in which areas are shaded or patterned according to a data variable. The variable is categorized into intervals, with each interval represented by a colour, and the map filled accordingly.
More about: Choropleth map
Choropleth map
# Loading required packages
library(unhcrthemes)
library(tidyverse)
library(scales)
library(sf)
# Load data
df <- read_csv("https://raw.githubusercontent.com/GDS-ODSSS/unhcr-dataviz-platform/master/data/geospatial/choropleth_map.csv")
poly_url <- "https://raw.githubusercontent.com/GDS-ODSSS/unhcr-dataviz-platform/master/data/geospatial/world_polygons_simplified.json"
line_url <- "https://raw.githubusercontent.com/GDS-ODSSS/unhcr-dataviz-platform/master/data/geospatial/world_lines_simplified.json"
# Add CRS to poly and join values from csv
poly <- read_sf(poly_url) |>
st_set_crs(4326) |>
left_join(df, by = c("color_code" = "iso3")) |>
mutate(legend = case_when(
refugees < 1e4 ~ "<10k",
refugees < 1e5 ~ "10k-100k",
refugees < 1e6 ~ "100k-1M",
is.na(refugees) ~ NA_character_,
TRUE ~ ">1M"
)) |>
mutate(legend = as_factor(legend) |>
fct_relevel("<10k", "10k-100k", "100k-1M", ">1M"))
# Sort line type
line <- read_sf(line_url) |>
mutate(
type = as_factor(type) |>
fct_relevel("solid", "dashed", "dotted", "dashed-dot")
) |>
st_set_crs(4326)
# Plot
ggplot() +
geom_sf(data = poly,
aes(fill = legend),
color = "transparent") +
geom_sf(data = line,
aes(linetype = type),
color = "white",
linewidth = .25,
show.legend = FALSE) +
coord_sf(crs = st_crs('ESRI:54030'),
expand = FALSE) +
scale_linetype_manual(values = c(1, 2, 3, 4)) +
scale_fill_unhcr_d(palette = "pal_blue") +
labs(
title = "Global refugee displacement by country of asylum | 2021",
caption = "The boundaries and names shown and the designations used on this map do not imply official\nendorsement or acceptance by the United Nations.\nSource: UNHCR Refugee Data Finder\n© UNHCR, The UN Refugee Agency"
) +
theme_unhcr_map(rel_small = .75,
rel_tiny = .65)
