lead-lag
From dplyr v0.7.8
by Hadley Wickham
Lead and lag.
Find the "next" or "previous" values in a vector. Useful for comparing values ahead of or behind the current values.
Usage
lead(x, n = 1L, default = NA, order_by = NULL, ...)lag(x, n = 1L, default = NA, order_by = NULL, ...)
Arguments
- x
a vector of values
- n
a 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
- ...
Needed for compatibility with lag generic.
Examples
# NOT RUN {
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)
# }
Community examples
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