geom_arrow_segment: Arrow segments
In ggarrow: Arrows for 'ggplot2'

geom_arrow_segment

R Documentation

Arrow segments

Description

geom_arrow_segment() draws a straight arrow between points (x, y) and (xend, yend). In contrast to geom_segment(), the xend and yend aesthetics default to x and y respectively, so only one of xend and yend is required.

Usage

geom_arrow_segment(
  mapping = NULL,
  data = NULL,
  stat = "identity",
  position = "identity",
  ...,
  arrow_head = arrow_head_wings(),
  arrow_fins = NULL,
  arrow_mid = NULL,
  length = 4,
  length_head = NULL,
  length_fins = NULL,
  length_mid = NULL,
  justify = 0,
  force_arrow = FALSE,
  mid_place = 0.5,
  resect = 0,
  resect_head = NULL,
  resect_fins = NULL,
  lineend = "butt",
  linejoin = "round",
  linemitre = 10,
  na.rm = FALSE,
  show.legend = NA,
  inherit.aes = TRUE
)

Arguments

`mapping`	Set of aesthetic mappings created by `aes()`. If specified and `inherit.aes = TRUE` (the default), it is combined with the default mapping at the top level of the plot. You must supply `mapping` if there is no plot mapping.
`data`	The data to be displayed in this layer. There are three options: If `NULL`, the default, the data is inherited from the plot data as specified in the call to `ggplot()`. A `data.frame`, or other object, will override the plot data. All objects will be fortified to produce a data frame. See `fortify()` for which variables will be created. A `function` will be called with a single argument, the plot data. The return value must be a `data.frame`, and will be used as the layer data. A `function` can be created from a `formula` (e.g. `~ head(.x, 10)`).
`stat`	The statistical transformation to use on the data for this layer. When using a `⁠geom_*()⁠` function to construct a layer, the `stat` argument can be used to override the default coupling between geoms and stats. The `stat` argument accepts the following: A `Stat` ggproto subclass, for example `StatCount`. A string naming the stat. To give the stat as a string, strip the function name of the `stat_` prefix. For example, to use `stat_count()`, give the stat as `"count"`. For more information and other ways to specify the stat, see the layer stat documentation.
`position`	A position adjustment to use on the data for this layer. This can be used in various ways, including to prevent overplotting and improving the display. The `position` argument accepts the following: The result of calling a position function, such as `position_jitter()`. This method allows for passing extra arguments to the position. A string naming the position adjustment. To give the position as a string, strip the function name of the `position_` prefix. For example, to use `position_jitter()`, give the position as `"jitter"`. For more information and other ways to specify the position, see the layer position documentation.
`...`	Other arguments passed on to `layer()`'s `params` argument. These arguments broadly fall into one of 4 categories below. Notably, further arguments to the `position` argument, or aesthetics that are required can not be passed through `...`. Unknown arguments that are not part of the 4 categories below are ignored. Static aesthetics that are not mapped to a scale, but are at a fixed value and apply to the layer as a whole. For example, `colour = "red"` or `linewidth = 3`. The geom's documentation has an Aesthetics section that lists the available options. The 'required' aesthetics cannot be passed on to the `params`. Please note that while passing unmapped aesthetics as vectors is technically possible, the order and required length is not guaranteed to be parallel to the input data. When constructing a layer using a `⁠stat_()⁠` function, the `...` argument can be used to pass on parameters to the `geom` part of the layer. An example of this is `stat_density(geom = "area", outline.type = "both")`. The geom's documentation lists which parameters it can accept. Inversely, when constructing a layer using a `⁠geom_()⁠` function, the `...` argument can be used to pass on parameters to the `stat` part of the layer. An example of this is `geom_area(stat = "density", adjust = 0.5)`. The stat's documentation lists which parameters it can accept. The `key_glyph` argument of `layer()` may also be passed on through `...`. This can be one of the functions described as key glyphs, to change the display of the layer in the legend.
`arrow_head`, `arrow_fins`, `arrow_mid`	A function call to one of the arrow ornament functions that can determine the shape of the arrow head, fins or middle (interior) arrows.
`length`, `length_head`, `length_fins`, `length_mid`	Determines the size of the arrow ornaments. `length` sets the default length, whereas `length_head`, `length_fins` and `length_mid` set the lengths of the arrow head, arrow fins or middle arrows respectively. Can be one of the following: A `⁠<numeric>⁠` to set the ornament size relative to the `⁠linewidth{_\*}⁠` settings. A `<unit>` to control the ornament size in an absolute manner. Behaviour of relative units such as `"npc"` or `"null"` is undefined.
`justify`	A `numeric(1)` between [0-1] to control where the arrows should be drawn relative to the path's endpoints. A value of `0` sets the arrow's tips at the path's end, whereas a value of `1` sets the arrow's base at the path's end.
`force_arrow`	A `logical(1)` which, if `TRUE` an arrow will be drawn even when the length of the arrow is shorter than the arrow heads and fins. If `FALSE`, will drop such arrows.
`mid_place`	Sets the location of middle (interior) arrows, when applicable. Can be one of the following: A `numeric` vector with values between [0-1] to set middle arrows at relative positions along the arc-length of a path. A `<unit>` to fill a path with arrows with the provided unit as distance between one arrow to the next.
`resect`, `resect_head`, `resect_fins`	A `numeric(1)` denoting millimetres or `<unit>` to shorten the arrow. `resect_head` shortens the arrow from the arrow head side, whereas `resect_fins` shortens the arrow from the fins side. Both inherit from `resect`.
`lineend`	Line end style (round, butt, square).
`linejoin`	Line join style (round, mitre, bevel).
`linemitre`	Line mitre limit (number greater than 1).
`na.rm`	If `FALSE`, the default, missing values are removed with a warning. If `TRUE`, missing values are silently removed.
`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. It can also be a named logical vector to finely select the aesthetics to display. To include legend keys for all levels, even when no data exists, use `TRUE`. If `NA`, all levels are shown in legend, but unobserved levels are omitted.
`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. `annotation_borders()`.

Value

A ⁠<Layer>⁠ ggproto object that can be added to a plot.

Aesthetics

geom_arrow_segment() understands the following aesthetics. Required aesthetics are displayed in bold and defaults are displayed for optional aesthetics:

•	`x`
•	`y`
•	`xend` or `yend`
•	`alpha`	→ `NA`
•	`arrow_fins`	→ `NULL`
•	`arrow_head`	→ `NULL`
•	`arrow_mid`	→ `NULL`
•	`colour`	→ via `theme()`
•	`group`	→ inferred
•	`linetype`	→ via `theme()`
•	`linewidth`	→ via `theme()`
•	`linewidth_fins`	→ `NULL`
•	`linewidth_head`	→ `NULL`
•	`resect_fins`	→ `NULL`
•	`resect_head`	→ `NULL`
•	`stroke_colour`	→ via `theme()`
•	`stroke_width`	→ via `theme()`

The linewidth_fins and linewidth_head inherit from linewidth. They can be used to seperately control the start- and end-width.

Learn more about setting these aesthetics in vignette("ggplot2-specs").

Examples

# Setup dummy data
set.seed(42)
df <- data.frame(
  x = LETTERS[1:6],
  y = 6:1 + rnorm(6)
)

# We can omit either `xend` or `yend` for this segment geom
p <- ggplot(df, aes(x, y = 0, yend = y, colour = x))
p + geom_arrow_segment()

# We can set the linewidth globally
p + geom_arrow_segment(aes(linewidth = y))

# Or seperately for the head and fins
p + geom_arrow_segment(aes(linewidth_head = y, linewidth_fins = 0))

# We can also place arrows in the middle
p + geom_arrow_segment(
  arrow_mid = arrow_head_line(), mid_place = c(0.33, 0.66),
  arrow_head = NULL # Turn off head
)

ggarrow documentation built on Sept. 14, 2025, 5:08 p.m.