lead-lag function

Compute lagged or leading values

Find the "previous" (lag()) or "next" (lead()) values in a vector. Useful for comparing values behind of or ahead of the current values.

lag(x, n = 1L, default = NULL, order_by = NULL, ...)

lead(x, n = 1L, default = NULL, order_by = NULL, ...)

Arguments

• x: A vector
• n: Positive integer of length 1, giving the number of positions to lag or lead by
• default: The value used to pad x back to its original size after the lag or lead has been applied. The default, NULL, pads with a missing value. If supplied, this must be a vector with size 1, which will be cast to the type of x.
• order_by: An optional secondary vector that defines the ordering to use when applying the lag or lead to x. If supplied, this must be the same size as x.
• ...: Not used.

Returns

A vector with the same type and size as x.

Examples

lag(1:5)
lead(1:5)

x <- 1:5
tibble(behind = lag(x), x, ahead = lead(x))

# If you want to look more rows behind or ahead, use `n`
lag(1:5, n = 1)
lag(1:5, n = 2)

lead(1:5, n = 1)
lead(1:5, n = 2)

# If you want to define a value to pad with, use `default`
lag(1:5)
lag(1:5, default = 0)

lead(1:5)
lead(1:5, default = 6)

# If the data are not already ordered, use `order_by`
scrambled <- slice_sample(
  tibble(year = 2000:2005, value = (0:5) ^ 2),
  prop = 1
)

wrong <- mutate(scrambled, previous_year_value = lag(value))
arrange(wrong, year)

right <- mutate(scrambled, previous_year_value = lag(value, order_by = year))
arrange(right, year)