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, order_by = NULL, ...)lead(x, n = 1L, default = NA, order_by = NULL, ...)
Vector of values
Positive integer of length 1, giving the number of positions to lead or lag by
Value used for non-existent rows. Defaults to NA.
Override the default ordering to use another vector or column
Needed for compatibility with lag generic.
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 for non-existing rows, use `default`
lag(1:5)
lag(1:5, default = 0)
lead(1:5)
lead(1:5, default = 6)
# If 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)
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