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 = NA)

lead(x, n = 1L, default = NA)

Arguments

x

A vector of values

n

A positive integer(1), giving the number of positions to lead or lag by.

default

The value used for non-existent rows (default: NA).

Examples

lag(1:5)
#> [1] NA 1 2 3 4
lead(1:5)
#> [1] 2 3 4 5 NA
x <- 1:5 data.frame(behind = lag(x), x, ahead = lead(x))
#> behind x ahead #> 1 NA 1 2 #> 2 1 2 3 #> 3 2 3 4 #> 4 3 4 5 #> 5 4 5 NA
# If you want to look more rows behind or ahead, use `n` lag(1:5, n = 1)
#> [1] NA 1 2 3 4
lag(1:5, n = 2)
#> [1] NA NA 1 2 3
lead(1:5, n = 1)
#> [1] 2 3 4 5 NA
lead(1:5, n = 2)
#> [1] 3 4 5 NA NA
# If you want to define a value for non-existing rows, use `default` lag(1:5)
#> [1] NA 1 2 3 4
lag(1:5, default = 0)
#> [1] 0 1 2 3 4
lead(1:5)
#> [1] 2 3 4 5 NA
lead(1:5, default = 6)
#> [1] 2 3 4 5 6