Assign cycling colour indices to trajectories

Creates a factor column that assigns each unique trajectory a colour index in the range `1:n`, cycling back to 1 after every `n` trajectories. When `panel_col` is supplied the cycle resets independently within each panel so that trajectory 1 in every panel gets index 1.

Usage

assign_cycle_colours(
  data,
  id_col,
  n,
  panel_col = NULL,
  out_col = "cycle_colour"
)

Arguments

data

A data frame containing at least `id_col` and, if supplied, `panel_col`.

id_col

Name of the column identifying individual trajectories.

n

Number of colours to cycle through (positive integer), or a character vector of colour values whose length determines `n`.

panel_col

Optional column name. When set the cycle restarts for each unique value of this column.

out_col

Name of the new factor column added to `data`. Default `"cycle_colour"`.

Value

`data` with an additional factor column named `out_col` (levels `"1"` through `"n"`).

Details

The resulting column can be passed to `colour_col` in [radiate()], [add_heading_points()], or [add_heading_vectors()] to keep colours consistent across layers.

Examples

df <- data.frame(id = paste0("T", 1:12), panel = rep(c("A","B"), each = 6))
df <- assign_cycle_colours(df, id_col = "id", n = 4, panel_col = "panel")
table(df$panel, df$cycle_colour)
#>    
#>     1 2 3 4
#>   A 2 2 1 1
#>   B 2 2 1 1