[R] basic indexing
Michaell Taylor
michaell.taylor at reis.com
Wed Oct 10 03:00:32 CEST 2001
I know there is a simple answer, I am attempting to make a simple indexing
issue too complex.
Suppose I have a dataframe like the following:
x y
1 5 8
2 8 9
3 1 2
4 6 8
5 9 8
Now suppose I simply wish to have a lagged indicator of x such that
x y z
1 5 8 NA
2 8 9 5
3 1 2 8
4 6 8 1
5 9 8 6
in stata this would be
gen z=x[N-1]
or even
x y z
1 5 8 NA
2 8 9 NA
3 1 2 NA
4 6 8 1
5 9 8 6
in stata this would be
gen z=x[N-1] if y==8
I've tried : z _ x[-1], but this leaves the vector too short. I could
"backfill" but this seem pretty contrived. In practice, I need to get
flexible lagging system as appropriate lags may depend of variable
combinations.
Thanks for any comments you may have.
Michaell
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