Dot density layer — viz_dotdensity • geovizr

The viz_dotdensity function creates a dot density map by distributing points proportionally to a numeric variable. Each dot represents a fixed quantity of the underlying data.

Usage

viz_dotdensity(
  map,
  data = NULL,
  var,
  stroke = "none",
  r = 1,
  dotval = NULL,
  fill = "black",
  legend = TRUE,
  leg_pos = NULL,
  leg_text = NULL,
  ...
)

Arguments

map: A geovizr map object created using viz_create().
data: A spatial data object, such as an `sf` object or a `terra::SpatVector`. Use data to enable iteration over features.
var: character. Name of the numeric variable used to generate dot density values.
stroke: character. Optional. Stroke color for dots (default "none").
r: numeric. Optional. Radius of each dot (default 1).
dotval: numeric. Optional. Value represented by a single dot. If not provided, it is computed automatically.
fill: character. Optional. Fill color of dots (default "black").
legend: logical. Optional. Whether to display legend (default TRUE).
leg_pos: numeric vector. Optional. Legend position (default c(10, svg.height - 10)).
leg_text: character. Optional. Legend text (default dot value).
...: Additional parameters passed to rendering or SVG container options.

Value

A modified `geoviz` map object with a new layer added. Rendering is performed using viz_render().

Examples

library(sf)
world <- st_read(
  system.file("gpkg/world.gpkg", package = "geovizr"),
  quiet = TRUE
)
cities <- st_read(
  system.file("gpkg/cities.gpkg", package = "geovizr"),
  quiet = TRUE
)

viz_create(projection = "EqualEarth") |>
  viz_path(datum = world, fill = "#f1f3f5") |>
  viz_dotdensity(data = cities, var = "population") |>
  viz_render()