https://github.com/hadley/dplyr
Tip revision: d1016a363adb2612a75e95e316084f4a33f723bb authored by Kirill Müller on 29 March 2018, 21:44:04 UTC
fledge: Bump version to 0.7.4.9003
fledge: Bump version to 0.7.4.9003
Tip revision: d1016a3
lead-lag.Rd
% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/lead-lag.R
\name{lead-lag}
\alias{lead-lag}
\alias{lead}
\alias{lag}
\title{Lead and lag.}
\usage{
lead(x, n = 1L, default = NA, order_by = NULL, ...)
lag(x, n = 1L, default = NA, order_by = NULL, ...)
}
\arguments{
\item{x}{a vector of values}
\item{n}{a positive integer of length 1, giving the number of positions to
lead or lag by}
\item{default}{value used for non-existent rows. Defaults to \code{NA}.}
\item{order_by}{override the default ordering to use another vector}
\item{...}{Needed for compatibility with lag generic.}
}
\description{
Find the "next" or "previous" values in a vector. Useful for comparing values
ahead of or behind the current values.
}
\examples{
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)
}