lead-lag: Compute lagged or leading values

In javifar/TIDYVERSE-DPLYR: A Grammar of Data Manipulation

Description

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

Usage

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

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

Arguments

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 NA.
order_by	Override the default ordering to use another vector or column
...	Needed for compatibility with lag generic.

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 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)

javifar/TIDYVERSE-DPLYR documentation built on Dec. 20, 2021, 9:08 p.m.