Chronological comparison of years

Tests whether years are chronologically earlier or later than each other, accounting for era direction.

Usage

yr_earlier_than(x, y)

yr_later_than(x, y)

yr_not_earlier_than(x, y)

yr_not_later_than(x, y)

Arguments

x, y

yr vectors with era. If in different eras, y is transformed to the era of x. Recycled to their common length.

Value

A logical vector.

Details

For forward-counting eras (e.g. CE), yr_earlier_than(x, y) is equivalent to x < y and yr_later_than(x, y) is equivalent to x > y. For backward-counting eras (e.g. BP, BCE), the comparisons are reversed.

yr_not_earlier_than() and yr_not_later_than() are the negations of yr_earlier_than() and yr_later_than(), equivalent to >= and <= respectively for forward-counting eras.

These are implemented as functions rather than S3 methods for <, >, <=, and >= to avoid surprises when numerical (i.e. not chronological) comparison is expected.

See also

Other functions for chronological ordering and extremes: yr_difference(), yr_extremes, yr_sort()

Examples

# Forward-counting era:
x <- yr(c(100, 200, 300), "CE")
yr_earlier_than(x, yr(200, "CE"))
#> [1]  TRUE FALSE FALSE
yr_later_than(x, yr(200, "CE"))
#> [1] FALSE FALSE  TRUE
yr_not_earlier_than(x, yr(200, "CE"))
#> [1] FALSE  TRUE  TRUE
yr_not_later_than(x, yr(200, "CE"))
#> [1]  TRUE  TRUE FALSE

# Backward-counting era:
y <- yr(c(100, 200, 300), "BCE")
yr_earlier_than(y, yr(200, "BCE"))
#> [1] FALSE FALSE  TRUE
yr_later_than(y, yr(200, "BCE"))
#> [1]  TRUE FALSE FALSE
yr_not_earlier_than(y, yr(200, "BCE"))
#> [1]  TRUE  TRUE FALSE
yr_not_later_than(y, yr(200, "BCE"))
#> [1] FALSE  TRUE  TRUE