Add a data-driven choropleth layer

Classifies column into class_count numeric ranges and colors each range from colormap, producing the same graduated symbology the application's Style panel builds from the interface.

Usage

add_choropleth(
  map,
  data,
  column,
  name = "Choropleth",
  class_count = 5,
  colormap = "viridis",
  scheme = c("equal-interval", "quantile"),
  style = list(),
  visible = TRUE,
  opacity = 1,
  ...
)

Arguments

map

A GeoLibre widget.

data

GeoJSON as a parsed list (a FeatureCollection, Feature, or bare geometry), a JSON string, a file path, an HTTP(S) URL, or an sf object. A URL or file is read and inlined into the project, up to a 50 MB limit; for larger datasets prefer add_vector(), which lets the browser stream the source.

column

Name of the numeric feature property to classify.

name

Layer name.

class_count

Number of classes, clamped to between 2 and 12.

colormap

A color ramp name from color_ramp_names().

scheme

Classification scheme, "equal-interval" or "quantile".

style

Named list of GeoLibre style overrides such as fillColor, strokeColor, and strokeWidth.

visible

Whether the layer is initially visible.

opacity

Layer opacity from zero to one.

...

Additional style overrides given as named arguments, merged into style. add_geojson(map, data, fillColor = "red") and add_geojson(map, data, style = list(fillColor = "red")) are equivalent.

Value

The modified widget.

See also

classify_layer() to symbolize a layer that is already on the map.

Examples

counties <- list(
  type = "FeatureCollection",
  features = list(
    list(
      type = "Feature", properties = list(pop = 100),
      geometry = list(type = "Point", coordinates = c(-77, 39))
    ),
    list(
      type = "Feature", properties = list(pop = 900),
      geometry = list(type = "Point", coordinates = c(-76, 40))
    )
  )
)
map <- geolibre() |>
  add_choropleth(counties, column = "pop", colormap = "blues", class_count = 3)
stopifnot(map$x$project$layers[[1]]$style$vectorStyleMode == "graduated")