add_north_arrow: Add a North arrow to a map

In edwardlavender/prettyGraphics: Pretty Graphics with R

Add a North arrow to a map

Description

This function adds a North arrow to a map.

Usage

add_north_arrow(
  x0 = "topleft",
  y0 = NULL,
  width,
  mid,
  height,
  type = c("filled head", "filled triangle", "arrow"),
  add_label = NULL,
  col = "black",
  ...
)

Arguments

x0, y0	A character keyword or doubles that define the arrow's position (see xy.coords).
width, mid, height	Arrow shape controls. Each argument accepts a double that defines the arrow width, mid-point or height. mid is only used for type = "filled head".
type	A character string that defines the arrow type. Currently supported options are (a) "filled head", which adds a (filled) arrow head (via polygon); (b) "filled triangle", which adds a (filled) triangle (via polygon); and (c) "arrow", which adds an arrow (via arrows).
add_label	A named list, passed to text, to add a label to the plot. add_label = NULL suppresses this option, add_label = list() implements default options and a named list customises these.
col, ...	Additional graphical parameters passed to polygon or arrows.

Details

Future functionality should include the capacity to control the tilt of the arrow (which is currently vertical) and to add north and east arrows that act as scale bars.

Value

The function adds an arrow to a map and invisibly returns a named list with the x and y coordinates of the arrow (derived from x0, y0, width, mid and height as applicable).

Author(s)

Edward Lavender

Examples

#### Example (1): Implement function using the default options
raster::plot(dat_gebco)
add_north_arrow()

#### Example (2): Adjust arrow location
raster::plot(dat_gebco)
add_north_arrow(x0 = "topright")
raster::plot(dat_gebco)
add_north_arrow(x0 = -5.55, y = 56.44)

#### Example (3): Adjust arrow type
raster::plot(dat_gebco)
add_north_arrow("topleft")
add_north_arrow("topright", type = "filled triangle")
add_north_arrow("center", type = "filled triangle")
add_north_arrow("right", type = "arrow")

#### Example (4): Adjust arrow type parameters
raster::plot(dat_gebco)
add_north_arrow("topleft", type = "filled triangle", border = "red")
add_north_arrow("center", type = "filled triangle", col = "blue")
add_north_arrow("top", type = "arrow", length = 0.05, lwd = 2)

#### Example (5): Add arrow label
raster::plot(dat_gebco)
add_north_arrow(add_label = list())

edwardlavender/prettyGraphics documentation built on Jan. 19, 2025, 2:47 p.m.