Arrow grob

Creates a graphical object that draws arrows. An arrow typically consists of three parts: the arrowhead, the shaft and fins. Relative to how an arrow is drawn from coordinates, these three parts describe the end, middle and beginning of an arrow line.

Usage

grob_arrow(
  x = unit(c(0, 1), "npc"),
  y = unit(c(0, 1), "npc"),
  id = NULL,
  id.lengths = NULL,
  arrow_head = arrow_head_wings(),
  arrow_fins = NULL,
  arrow_mid = NULL,
  length_head = unit(5, "mm"),
  length_fins = NULL,
  length_mid = NULL,
  justify = 0,
  shaft_width = unit(1, "mm"),
  mid_place = 0.5,
  resect = unit(0, "mm"),
  resect_fins = NULL,
  resect_head = NULL,
  force_arrow = FALSE,
  default.units = "mm",
  name = NULL,
  gp = gpar(),
  vp = NULL
)

Arguments

x

A numeric vector or unit object specifying x-values.

y

A numeric vector or unit object specifying y-values.

id

A numeric vector used to separate locations in x and y into multiple lines. All locations with the same id belong to the same line.

id.lengths

A numeric vector used to separate locations in x and y into multiple lines. Specifies consecutive blocks of locations which make up separate lines.

arrow_head, arrow_fins, arrow_mid

A <matrix[n, 2]>, such as those returned by arrow ornament functions, giving arrow shapes. The matrix can (should) have the notch_angle attribute that will be used to fuse the shaft to the arrow ornaments. If NULL, no ornament will be drawn.

length_head, length_fins, length_mid

A <unit> object controlling the size of the arrow ornaments.

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.

shaft_width

A <unit> object controlling the width of the arrow's shaft.

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_fins, resect_head

A <unit> object that can be used to create an offset between the endings of the coordinates and where the arrow will be displayed visually. resect_fins and resect_head control this offset at the start and end of the arrow respectively and both default to resect.

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.

default.units

A string indicating the default units to use if x or y are only given as numeric vectors.

name

A character identifier.

gp

An object of class "gpar", typically the output from a call to the function gpar. This is basically a list of graphical parameter settings.

vp

A Grid viewport object (or NULL).

Value

A <arrow_path>

graphical object.

Examples

requireNamespace("grid")

# Creating an arrow
arrow <- grob_arrow(
  x = unit(c(0.2, 0.5, 0.8, 0.2, 0.5, 0.8), "npc"),
  y = unit(c(0.2, 0.8, 0.2, 0.8, 0.2, 0.8), "npc"),
  id.lengths  = c(3, 3),
  arrow_head  = arrow_head_wings(),
  arrow_fins  = arrow_fins_feather(),
  length_fins = 8,
  shaft_width = 1,
  gp = grid::gpar(fill = c("dodgerblue", "tomato"), col = "black")
)

# Drawing the arrow
grid::grid.newpage(); grid::grid.draw(arrow)