Map decorations

Cartographic furniture for coord_sf() maps. mark_scalebar() draws a segmented distance bar; mark_compass() draws a north arrow. Both are fixed-position decorations pinned to a panel corner (they take no data aesthetics). Graticule lines (meridians and parallels) are added through coord_sf()'s graticule argument, not a mark, so they render behind the map.

Usage

mark_scalebar(
  plot,
  distance = NULL,
  unit = "km",
  position = "bottomleft",
  segments = 4L,
  height = 2.5,
  pad = 4,
  text_size = 7,
  color = "black",
  fill = "white",
  data = NULL
)

mark_compass(
  plot,
  position = "topright",
  size = 10,
  pad = 4,
  rotation = 0,
  color = "black",
  fill = "black",
  text = TRUE,
  data = NULL
)

Arguments

plot

A PlotSpec.

distance

Bar length in unit. NULL (default) picks a round number near a quarter of the panel width.

unit

Distance unit for the label and distance: "km" (default), "m", "mi", or "ft".

position

Panel corner to anchor the decoration: "bottomleft" (scale bar default), "topright" (compass default), "bottomright", or "topleft" (the abbreviations "bl"/"br"/"tl"/ "tr" also work).

segments

Number of alternating segments in the bar (default 4).

height

Bar thickness, in millimetres.

pad

Inset from the panel edge, in millimetres.

text_size

Label font size (points).

color, fill

Stroke and fill colours. For the scale bar the segments alternate color and fill; for the compass the arrow is fill with a color outline.

data

Optional layer data (rarely needed – decorations are not data-driven).

size

Glyph height, in millimetres.

rotation

Extra clockwise rotation of the arrow, in degrees (e.g. to point at grid north on a rotated layout).

text

Draw the "N" label above the arrow (default TRUE).

Value

The modified PlotSpec.

See also

coord_sf(), mark_sf()

Examples

if (FALSE) { # \dontrun{
nc <- sf::st_read(system.file("shape/nc.shp", package = "sf"), quiet = TRUE)
vplot(nc) |>
  mark_sf(fill = BIR74) |>
  coord_sf(crs = 3857, graticule = TRUE) |>
  mark_scalebar() |>
  mark_compass()
} # }