Reference arrows on the margins

Small arrows on plot margins can supplement a 2d display with annotations. Arrows can be used to highlight specific values along a margin. The geometries geom_x_margin_arrow() and geom_y_margin_arrow() behave similarly geom_vline() and geom_hline() and share their "double personality" as both annotations and geometries.

geom_x_margin_arrow(
  mapping = NULL,
  data = NULL,
  stat = "identity",
  position = "identity",
  ...,
  xintercept,
  sides = "b",
  arrow.length = 0.03,
  na.rm = FALSE,
  show.legend = FALSE,
  inherit.aes = FALSE
)

geom_y_margin_arrow(
  mapping = NULL,
  data = NULL,
  stat = "identity",
  position = "identity",
  ...,
  yintercept,
  sides = "l",
  arrow.length = 0.03,
  na.rm = FALSE,
  show.legend = FALSE,
  inherit.aes = FALSE
)

Arguments

mapping

The aesthetic mapping, usually constructed with aes. Only needs to be set at the layer level if you are overriding the plot defaults.

data

A layer specific dataset - only needed if you want to override the plot defaults.

stat

The statistical transformation to use on the data for this layer, as a string.

position

Position adjustment, either as a string, or the result of a call to a position adjustment function.

...

other arguments passed on to layer. This can include aesthetics whose values you want to set, not map. See layer for more details.

xintercept, yintercept

numeric Parameters that control the position of the marginal points. If these are set, data, mapping and show.legend are overridden.

sides

A string that controls which sides of the plot the rugs appear on. It can be set to a string containing any combination of "trbl", for top, right, bottom, and left.

arrow.length

numeric value expressed in npc units for the length of the arows inwards from the edge of the plotting area.

na.rm

If FALSE (the default), removes missing values with a warning. If TRUE silently removes missing values.

show.legend

logical. Should this layer be included in the legends? NA, the default, includes if any aesthetics are mapped. FALSE never includes, and TRUE always includes.

inherit.aes

If FALSE, overrides the default aesthetics, rather than combining with them. This is most useful for helper functions that define both data and aesthetics and shouldn't inherit behaviour from the default plot specification, e.g., borders.

Value

A plot layer instance.

See also

Other Geometries for marginal annotations in ggplots: geom_x_margin_grob(), geom_x_margin_point()

Examples

p <- ggplot(mtcars, aes(wt, mpg)) +
  geom_point()
p

p + geom_x_margin_arrow(xintercept = 3.5)

p + geom_y_margin_arrow(yintercept = c(18, 28, 15))

p + geom_x_margin_arrow(data = data.frame(x = c(2.5, 4.5)),
                        mapping = aes(xintercept = x))

p + geom_x_margin_arrow(data = data.frame(x = c(2.5, 4.5)),
                        mapping = aes(xintercept = x),
                        sides="tb")