Shift factor levels to left or right, wrapping around at end

Source: R/shift.R

This is useful when the levels of an ordered factor are actually cyclical, with different conventions on the starting point.

fct_shift(f, n = 1L)

Arguments

f

A factor.
n

Positive values shift to the left; negative values shift to the right.

Examples

x <- factor(
  c("Mon", "Tue", "Wed"),
  levels = c("Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"),
  ordered = TRUE
)
x
#> [1] Mon Tue Wed
#> Levels: Sun < Mon < Tue < Wed < Thu < Fri < Sat
fct_shift(x)
#> [1] Mon Tue Wed
#> Levels: Mon < Tue < Wed < Thu < Fri < Sat < Sun
fct_shift(x, 2)
#> [1] Mon Tue Wed
#> Levels: Tue < Wed < Thu < Fri < Sat < Sun < Mon
fct_shift(x, -1)
#> [1] Mon Tue Wed
#> Levels: Sat < Sun < Mon < Tue < Wed < Thu < Fri