time_id: Time ID

In timeplyr: Fast Tidy Tools for Date and Date-Time Manipulation

Time ID

Description

Generate a time ID that signifies how many time steps away a time value is from the starting time point or more intuitively, this is the time passed since the first time point.

Usage

time_id(
  x,
  time_by = NULL,
  g = NULL,
  na_skip = TRUE,
  time_type = getOption("timeplyr.time_type", "auto"),
  shift = 1L
)

Arguments

x	Time variable. Can be a Date, POSIXt, numeric, integer, yearmon, or yearqtr.
time_by	Time unit. This signifies the granularity of the time data with which to measure gaps in the sequence. If your data is daily for example, supply time_by = "days". If weekly, supply time_by = "week". Must be one of the three: string, specifying either the unit or the number and unit, e.g time_by = "days" or time_by = "2 weeks" named list of length one, the unit being the name, and the number the value of the list, e.g. list("days" = 7). For the vectorized time functions, you can supply multiple values, e.g. list("days" = 1:10). Numeric vector. If time_by is a numeric vector and x is not a date/datetime, then arithmetic is used, e.g time_by = 1.
g	Object used for grouping x. This can for example be a vector or data frame. g is passed directly to collapse::GRP().
na_skip	Should NA values be skipped? Default is TRUE.
time_type	If "auto", periods are used for the time expansion when days, weeks, months or years are specified, and durations are used otherwise.
shift	Value used to shift the time IDs. Typically this is 1 to ensure the IDs start at 1 but can be 0 or even negative if for example your time values are going backwards in time.

Details

This is heavily inspired by collapse::timeid but differs in 3 ways:

• The time steps need not be the greatest common divisor of successive differences

• The starting time point may not necessarily be the earliest chronologically and thus time_id can generate negative IDs.

• g can be supplied to calculate IDs by group.

time_id(c(3, 2, 1)) is not the same as collapse::timeid(c(3, 2, 1)). In general time_id(sort(x)) should be equal to collapse::timeid(sort(x)). The time difference GCD is always calculated using all the data and not by-group.

Value

An integer vector the same length as x.

See Also

time_elapsed time_seq_id

timeplyr documentation built on Sept. 12, 2024, 7:37 a.m.