X-scale for periodic longitudinal plots

This is a convenience wrapper around ggplot2::scale_x_continuous() that enforces limits = c(0, period) and uses oob = scales::oob_keep.

Usage

scale_x_kodom_periodic(period = 12, breaks = 1:period, ...)

Arguments

period

The length of one complete cycle (e.g. 12 for months). Must match the period argument passed to geom_kodom_periodic(). Default 12.

breaks

Passed to scale_x_continuous(). Default provides integer breaks for the period.

...

Additional arguments passed to ggplot2::scale_x_continuous(), such as labels.

Value

A ggplot2::scale_x_continuous() object.

Details

Why is this necessary? To make exactly one cycle span exactly one 360-degree rotation in coord_polar, the scale limits must be set to the period length (e.g., c(0, 12)). However, standard ggplot2 scale_x_continuous will drop any data outside those limits. By setting oob = scales::oob_keep, we instruct ggplot2 to keep the data that exceeds the period. coord_polar then natively wraps those out-of-bounds values around the circle, creating beautiful, continuous Archimedean spirals!

Examples

# \donttest{
library(ggplot2)
df <- data.frame(
  subject_id = rep(1:5, each = 4),
  time = rep(1:4, 5),
  visit_month = rep(1:4, 5),
  value = rep(1:4, 5),
  hba1c = rep(1:4, 5),
  arm = rep(c("Treatment", "Control"), c(12, 8))
)
ggplot(df, aes(x = visit_month, id = subject_id, colour = hba1c)) +
  geom_kodom_periodic(period = 12) +
  scale_x_kodom_periodic(period = 12, labels = month.abb) +
  scale_y_kodom_periodic() +
  coord_kodom_periodic() +
  theme_kodom_periodic()

# }