.BG
.FN lag
.TL
Create a Lagged Time-Series
.CS
lag(x, k=1)
.AG x
a time-series.  Missing values (`NA's) are allowed.
.AG k
the number of positions the new series is to lag the input
series; negative value will lead the series.
.br
.ne 4
.RT
a time-series of the same length as `x' but lagged by `k'
positions.  Only the start and end dates are changed; the
series still has the same number of observations.
.SA
`tsmatrix' for aligning the time domains of several series.
.EX
l12gnp <- lag(gnp,12) # gnp lagged by 12 months
.KW ts
.WR
