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Label sf features at their interior point

Source: R/marks.R
mark_sf_label.Rd

mark_sf_label() draws one text label per sf feature, placed at the feature's interior point (sf::st_point_on_surface(), guaranteed to fall inside each polygon — unlike a centroid, which can land in a bay or a hole). The label points are reprojected through the same coord_sf CRS as mark_sf(), so they always land where the geometry is drawn. Layer it over a mark_sf() choropleth to name the regions; repel = TRUE (the default) pushes crowded labels apart.

Usage

mark_sf_label(
  plot,
  ...,
  size = NULL,
  repel = TRUE,
  box_padding = 1,
  min_segment_length = 2,
  blend = NULL,
  data = NULL
)

Arguments

plot

A PlotSpec (from vplot()).

...

Encodings (tidy-eval): the label to draw at each feature, plus an optional color / size. The position comes from the geometry, so x / y are not mapped.

size

Font size in points.

repel

Move overlapping labels apart (force-directed, ggrepel-style), with leader lines to the points? Single cartesian panel only.

box_padding

Extra space (mm) kept around each label box during repulsion.

min_segment_length

Shortest leader line (mm) worth drawing; a label that barely moved gets none.

blend

Optional blend mode for compositing this layer against what is already drawn beneath it (the panel and earlier layers), one of the CSS mix-blend-mode names, e.g. "multiply", "screen", "darken". The whole layer composites as one isolated group (not per element).

data

An sf data frame (defaults to the plot's). Its geometry supplies the label positions.

Value

The modified PlotSpec.

See also

mark_sf(), mark_text()

Examples

if (requireNamespace("sf", quietly = TRUE)) {
  nc <- sf::st_read(system.file("shape/nc.shp", package = "sf"), quiet = TRUE)
  vplot(nc) |>
    mark_sf(fill = AREA) |>
    mark_sf_label(label = NAME, size = 5)
}