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 = NA, order_by = NULL, ...) lead(x, n = 1L, default = NA, order_by = NULL, ...)
x |
Vector of values |
n |
Positive integer of length 1, giving the number of positions to lead or lag by |
default |
Value used for non-existent rows. Defaults to |
order_by |
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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