A small line chart for every country, on the tile grid

Every country's trajectory in a panel at once: a sparkline per country, placed on the bundled equal-area world_tiles grid, so Europe and the Caribbean are as readable as Russia. It is the glyph-map idea (Wickham, Hofmann, Wickham & Cook 2012) on a grid of equal cells, which removes the overlap glyphs at country centroids suffer where countries are small and close together.

Usage

tile_trend_map(
  data,
  value,
  years = NULL,
  label = TRUE,
  scales = c("free_y", "fixed"),
  footnote = "auto"
)

Arguments

data: A panel with iso3c, year and the value column, one row per country and year.
value: The column to draw (unquoted).
years: Optional years to draw: a range c(from, to), or the years themselves. NULL (default) draws every year in data.
label: Whether to print each tile's ISO code (default TRUE).
scales: "free_y" (default) draws each country on its own scale, so every line shows its own shape; "fixed" puts every country on one scale, so the lines can be compared in level as well as shape. The subtitle says which.
footnote: The caption, as in world_map(): "auto" (default) says how many countries have a line.

Value

A ggplot object. A country needs two years with values to have a line; one with fewer, or with no tile (see world_tiles), counts as missing in the caption and in map_provenance().

Backend

Drawn on the bundled equal-area tile grid (world_tiles), one square per country; no geometry backend is involved.

References

Wickham, H., Hofmann, H., Wickham, C. & Cook, D. (2012). Glyph-maps for visually exploring temporal patterns in climate data and models. Environmetrics 23(5), 382-393. doi:10.1002/env.2152

Examples

# \donttest{
set.seed(1)
pan <- expand.grid(iso3c = countryatlas::world_tiles$iso3c, year = 2000:2020)
pan$v <- stats::ave(stats::rnorm(nrow(pan)), pan$iso3c, FUN = cumsum)
tile_trend_map(pan, v)

# }