Add heading vector segments from inner crossing to unit circle

Draws a segment from the inner-radius crossing position to the heading endpoint on the unit circle for each row of a headings data frame. This visualises the extrapolated vector used to derive the heading and mirrors the dotted-line display in the original millipede tracking workflow.

Usage

add_heading_vectors(
  headings_df,
  colour_col = NULL,
  colour = NULL,
  linetype = "dotted"
)

Arguments

headings_df

Data frame with columns `heading` (radians), `x_inner`, and `y_inner`.

colour_col

Name of a column in `headings_df` to map to the colour aesthetic. When `NULL` (default), the value of `attr(headings_df, "colour_col")` is used if set – so vectors automatically inherit the colour mapping from the associated trajectory plot when that attribute is present. Ignored when `colour` is supplied.

colour

Fixed colour string. Overrides `colour_col` when supplied; when `NULL` and no `colour_col` resolves, defaults to `"black"`.

linetype

Line type string or integer passed to `geom_segment`.

Value

A `geom_segment()` layer.

Details

Requires columns `heading`, `x_inner`, and `y_inner`, which are present when [derive_headings()] is called with `rule = "crossing"` and `return_coords = TRUE`.

See also

[add_heading_points()], [derive_headings()]

Examples

library(ggplot2)
hd <- data.frame(id = "A", time = 1, heading = pi / 4,
                 x_inner = 0.15, y_inner = 0.15)
ggplot() + coord_fixed() + add_heading_vectors(hd)