Lag {Hmisc}

Lag a Numeric, Character, or Factor Vector

Description

Shifts a vector shift elements later. Character or factor variables are padded with "", numerics with NA. The shift may be negative.

Usage

Lag(x, shift = 1)

Arguments

x

a vector

shift

integer specifying the number of observations to be shifted to the right. Negative values imply shifts to the left.

Details

A.ttributes of the original object are carried along to the new lagged one.

Value

a vector like x

Author(s)

Frank Harrell

See Also

lag

Examples

Lag(1:5,2)
Lag(letters[1:4],2)
Lag(factor(letters[1:4]),-2)
# Find which observations are the first for a given subject
id <- c('a','a','b','b','b','c')
id != Lag(id)
!duplicated(id)