returns a subsample of a panel data set; in particular drops
all observations that are not in keepids. If it is not set,
randomly keeps nkeep observations.
Usage
subsample(dta, idname, tname, keepids = NULL, nkeep = NULL)
Arguments
- dta
a data.frame which is a balanced panel
- idname
the name of the id variable
- tname
the name of the time variable
- keepids
which ids to keep
- nkeep
how many ids to keep (only used if keepids
is not set); the default is the number of unique ids
Value
a data.frame that contains a subsample of dta
Examples
data("LaborSupply", package = "plm")
nrow(LaborSupply)
#> [1] 5320
unique(LaborSupply$year)
#> [1] 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988
ss <- subsample(LaborSupply, "id", "year", nkeep = 100)
nrow(ss)
#> [1] 1000
