geom_azimuth: Azimuth visualization

In tectonicr: Analyzing the Orientation of Maximum Horizontal Stress

Azimuth visualization

Description

geom_azimuth() visualizes axial-directional vector fields using a geom to produce a new graphical layer, which allows aesthetic options. This layer can be overlaid on a map to improve visualisation of mapped data. The geom draws line segments (spokes) centered at (x, y) with a given orientation (angle in degrees) and length (radius). By default the spoke is centered using PositionCenterSpoke, so that the given coordinates mark the middle of the line. The azimuths are given as angles in degrees increasing clockwise from North.

Usage

geom_azimuth(
  mapping = NULL,
  data = NULL,
  stat = "azimuth",
  center = TRUE,
  radius = NULL,
  na.rm = FALSE,
  show.legend = NA,
  inherit.aes = TRUE,
  ...
)

Arguments

mapping	Set of aesthetic mappings created by ggplot2::aes().
data	A data frame. If NULL, the default, the data is inherited from the plot data as specified in the call to ggplot2::ggplot().
stat	The statistical transformation to use on the data. Defaults to "identity".
center	Logical; if TRUE (the default) spokes are centered on (x, y) using PositionCenterSpoke - useful for axial data. If FALSE, behaves like ggplot2::geom_spoke() (line starts at (x, y)) - useful for directional data (especially when in combination with arrow()).
radius	Length of spoke
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?
inherit.aes	If FALSE, overrides the default aesthetics, rather than combining with them.
...	Other arguments passed on to ggplot2::layer(). These are often aesthetics (e.g. colour, linetype, linewidth, alpha).

Value

A ggplot2 layer that adds axis-like spokes.

Aesthetics

geom_azimuth() understands the following aesthetics (required aesthetics in bold):

• x

• y

• angle (in degrees, transformed internally)

• radius

• colour

• alpha

• linewidth

• linetype

See Also

ggplot2::geom_spoke(), geom_azimuthpoint()

Examples

set.seed(20250411)
df <- data.frame(
  x = runif(5), y = runif(5),
  angle_deg = rvm(5, mean = 90, kappa = 10),
  radius = runif(5, 0.1, 2)
)

if (require("ggplot2")) {
  ggplot(df, aes(x, y)) +
    geom_azimuth(aes(angle = angle_deg), radius = .1, linewidth = 1.2, colour = "blue")
  if (require("grid")) {
    ggplot(df, aes(x, y, radius = radius)) +
      geom_azimuth(aes(angle = angle_deg), center = FALSE, colour = "red", arrow = grid::arrow())
  }
}

tectonicr documentation built on Dec. 12, 2025, 9:06 a.m.