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Comparison operators for cyclical time (mt_cyclical)

Source: R/compare.R
mt_cyclical-compare.Rd

A cyclical time value stores an absolute chronon count but means a position within its cycle (e.g. day_of_week() means a weekday, not a particular Wednesday). Comparison therefore reduces both operands to their position within the cycle - the same reduction format() displays - and compares those:

  • day_of_week(date("2020-01-15")) == day_of_week(date("2020-01-22")) is TRUE, since both are a Wednesday.

  • day_of_year(date("2020-01-15")) == day_of_year(date("2021-01-15")) is TRUE, since both are the 15th day of their year.

Both operands must share a cycle: a cycle is a modulus rather than a unit, so there is no meaningful common cycle between (say) a weekday and a day-of-year, and comparing them is an error. Differing chronons within a shared cycle are reconciled as they are for mt_linear: both positions are expressed in the finest common chronon, and a discrete value spans the closed interval of its chronon, so

  • a == b iff start(a) == start(b) and end(a) == end(b)

  • a < b iff end(a) < start(b), a > b iff start(a) > end(b)

  • a <= b iff end(a) <= end(b), a >= b iff start(a) >= start(b)

As for mt_linear, this is not a total order when chronons differ. Ordering follows the position within the cycle (so Mon < Wed); the cycle's wrap-around is not treated as circular.

Usage

# S4 method for class 'mt_cyclical'
e1 == e2
# S4 method for class 'mt_cyclical'
e1 != e2
# S4 method for class 'mt_cyclical'
e1 < e2
# S4 method for class 'mt_cyclical'
e1 <= e2
# S4 method for class 'mt_cyclical'
e1 > e2
# S4 method for class 'mt_cyclical'
e1 >= e2

Arguments

e1, e2

mt_cyclical vectors sharing a cycle (or values castable to one, such as plain numeric vectors sharing the other operand's chronon).

Value

A logical vector.