A function to check whether treatment is staggered in a panel data set; that is, whether treatment is absorbing, so that no unit ever reverts from treated back to untreated.
Arguments
- df
the data.frame used in the function
- idname
name of column that holds the unit id
- treatname
name of column with the treatment indicator
- tname
name of column that holds the time period. If supplied, each unit's rows are sorted by it before checking. If `NULL` (the default), the rows are assumed to already be in time order.
Examples
n <- 50
id <- rep(seq_len(n), each = 4)
t <- rep(1:4, n)
g <- rep(sample(c(0, 2, 3), n, replace = TRUE), each = 4)
treat <- as.integer(t >= g & g > 0)
dta <- data.frame(id = id, t = t, treat = treat)
check_staggered(dta, idname = "id", treatname = "treat")
#> [1] TRUE
## treatment that switches back off is not staggered
dta_rev <- data.frame(
id = c(1, 1, 2, 2), t = c(1, 2, 1, 2), treat = c(0, 1, 1, 0)
)
check_staggered(dta_rev, idname = "id", treatname = "treat")
#> [1] FALSE