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Detect changes in a date time vector

Source: R/change.R
warp_change.Rd

warp_change() detects changes at the period level.

If last = TRUE, it returns locations of the last value before a change, and the last location in x is always included. Additionally, if endpoint = TRUE, the first location in x will be included.

If last = FALSE, it returns locations of the first value after a change, and the first location in x is always included. Additionally, if endpoint = TRUE, the last location in x will be included.

Usage

warp_change(
  x,
  period,
  ...,
  every = 1L,
  origin = NULL,
  last = TRUE,
  endpoint = FALSE
)

Arguments

x

[Date / POSIXct / POSIXlt]

A date time vector.

period

[character(1)]

A string defining the period to group by. Valid inputs can be roughly broken into:

  • "year", "quarter", "month", "week", "day"

  • "hour", "minute", "second", "millisecond"

  • "yweek", "mweek"

  • "yday", "mday"

...

[dots]

These dots are for future extensions and must be empty.

every

[positive integer(1)]

The number of periods to group together.

For example, if the period was set to "year" with an every value of 2, then the years 1970 and 1971 would be placed in the same group.

origin

[Date(1) / POSIXct(1) / POSIXlt(1) / NULL]

The reference date time value. The default when left as NULL is the epoch time of 1970-01-01 00:00:00, in the time zone of the index.

This is generally used to define the anchor time to count from, which is relevant when the every value is > 1.

last

[logical(1)]

If TRUE, the last location before a change is returned. The last location of the input is always returned.

If FALSE, the first location after a change is returned. The first location of the input is always returned.

endpoint

[logical(1)]

If TRUE and last = TRUE, will additionally return the first location of the input.

If TRUE and last = FALSE, will additionally return the last location of the input.

If FALSE, does nothing.

Value

A double vector of locations.

Examples

x <- as.Date("2019-01-01") + 0:5
x
#> [1] "2019-01-01" "2019-01-02" "2019-01-03" "2019-01-04" "2019-01-05"
#> [6] "2019-01-06"

# Last location before a change, last location of `x` is always included
warp_change(x, period = "yday", every = 2, last = TRUE)
#> [1] 2 4 6

# Also include first location
warp_change(x, period = "yday", every = 2, last = TRUE, endpoint = TRUE)
#> [1] 1 2 4 6

# First location after a change, first location of `x` is always included
warp_change(x, period = "yday", every = 2, last = FALSE)
#> [1] 1 3 5

# Also include last location
warp_change(x, period = "yday", every = 2, last = FALSE, endpoint = TRUE)
#> [1] 1 3 5 6