continuous_arrow_scales {ggarrow}

Continuous arrow scales

Description

These scales can map continuous input to an argument of an arrow generator. The arrow head, arrow fins and middle arrows have separate scales and by default use different generators.

Usage

scale_arrow_head_continuous(
  name = waiver(),
  breaks = waiver(),
  labels = waiver(),
  limits = NULL,
  generator = arrow_head_wings,
  map_arg = "offset",
  other_args = list(),
  range = c(10, 80),
  transform = "identity",
  guide = "legend"
)

scale_arrow_fins_continuous(
  name = waiver(),
  breaks = waiver(),
  labels = waiver(),
  limits = NULL,
  generator = arrow_fins_feather,
  map_arg = "indent",
  other_args = list(),
  range = c(0, 1),
  transform = "identity",
  guide = "legend"
)

scale_arrow_mid_continuous(
  name = waiver(),
  breaks = waiver(),
  labels = waiver(),
  limits = NULL,
  generator = arrow_head_wings,
  map_arg = "offset",
  other_args = list(),
  range = c(10, 80),
  transform = "identity",
  guide = "legend"
)

Arguments

name

The name of the scale. Used as the axis or legend title. If waiver(), the default, the name of the scale is taken from the first mapping used for that aesthetic. If NULL, the legend title will be omitted.

breaks

One of:

• NULL for no breaks

• waiver() for the default breaks computed by the transformation object

• A numeric vector of positions

• A function that takes the limits as input and returns breaks as output (e.g., a function returned by scales::extended_breaks()). Note that for position scales, limits are provided after scale expansion. Also accepts rlang lambda function notation.

labels

One of:

• NULL for no labels

• waiver() for the default labels computed by the transformation object

• A character vector giving labels (must be same length as breaks)

• An expression vector (must be the same length as breaks). See ?plotmath for details.

• A function that takes the breaks as input and returns labels as output. Also accepts rlang lambda function notation.

limits

One of:

• NULL to use the default scale range

• A numeric vector of length two providing limits of the scale. Use NA to refer to the existing minimum or maximum

• A function that accepts the existing (automatic) limits and returns new limits. Also accepts rlang lambda function notation. Note that setting limits on positional scales will remove data outside of the limits. If the purpose is to zoom, use the limit argument in the coordinate system (see coord_cartesian()).

generator

A ⁠<function>⁠ that can create an arrow ornament, such as ornamentation functions.

map_arg

An argument of the generator function to map input to.

other_args

Additional, fixed, arguments to pass to the generator.

range

The range that generator's map_arg may take

transform

For continuous scales, the name of a transformation object or the object itself. Built-in transformations include "asn", "atanh", "boxcox", "date", "exp", "hms", "identity", "log", "log10", "log1p", "log2", "logit", "modulus", "probability", "probit", "pseudo_log", "reciprocal", "reverse", "sqrt" and "time".

A transformation object bundles together a transform, its inverse, and methods for generating breaks and labels. Transformation objects are defined in the scales package, and are called ⁠transform_<name>⁠. If transformations require arguments, you can call them from the scales package, e.g. scales::transform_boxcox(p = 2). You can create your own transformation with scales::new_transform().

guide

A function used to create a guide or its name. See guides() for more information.

Value

A ⁠<Scale>⁠ that can be added to a plot.

Examples

base <- ggplot(whirlpool(5), aes(x, y, colour = group)) +
  coord_fixed()

p <- base +
  geom_arrow(
    aes(arrow_head = as.integer(group)),
    length_head = 10
  )

# A typical scale
p + scale_arrow_head_continuous()

# Change other arguments passed to the generator
p + scale_arrow_head_continuous(other_args = list(inset = 90))

# Using another argument of the generator
p + scale_arrow_head_continuous(name = "inset",  map_arg = "inset")

# Using a different generator
p + scale_arrow_head_continuous(
  generator = arrow_head_line,
  map_arg = "angle",
  range = c(20, 80)
)

# The same goes for other arrow aesthetics, but the `generator()` might
# differ.
base +
  geom_arrow(
    aes(arrow_fins = as.integer(group), arrow_mid = as.integer(group)),
    length_fins = 10, arrow_head = NULL
  ) +
  scale_arrow_fins_continuous(map_arg = "height", range = c(0.1, 1)) +
  scale_arrow_mid_continuous(map_arg = "inset")