Lead and lag.
Lead and lag are useful for comparing values offset by a constant (e.g. the previous or next value)
lead(x, n = 1L, default = NA, order_by = NULL)
lag(x, n = 1L, default = NA, order_by = NULL)
- a vector of values
- a postive integer of length 1, giving the number of positions to lead or lag by
- value used for non-existant rows. Defaults
- override the default ordering to use another vector
lead(1:10, 1) lead(1:10, 2) lag(1:10, 1) lead(1:10, 1) x <- runif(5) cbind(ahead = lead(x), x, behind = lag(x)) # Use order_by if data not already ordered df <- data.frame(year = 2000:2005, value = (0:5) ^ 2) scrambled <- df[sample(nrow(df)), ] wrong <- mutate(scrambled, prev = lag(value)) arrange(wrong, year) right <- mutate(scrambled, prev = lag(value, order_by = year)) arrange(right, year)
Looks like there are no examples yet.