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

shift

""

NA

Lag(x, shift = 1)

a vector like x

x

a vector

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

Frank Harrell

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

lag

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)

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