Every lg_df accumulates the sequence of lg_filter(), lg_derive(),
and lg_join() operations that produced it, in its lg_history
attribute. lg_history() returns that sequence directly rather than
requiring attr(data, "lg_history").
Value
An lg_history object (a list of lg_operation records applied
to this specific object, in the order they were applied; empty if
none yet). Iterate over it, or index into it, exactly like a regular
list — the class only changes how it prints.
Details
The returned object prints as a readable summary rather than a raw nested
list — when empty, it reports plainly that no operations are recorded for
this object yet, rather than printing a bare, uninformative list().
Examples
lg_start()
#> lineager: session started
dm <- lg_tag(
data.frame(USUBJID = c("01", "02"), AGE = c(20L, 15L)),
dataset_id = "DM"
)
#> lineager: tagged 'DM' — 2 rows, 2 cols
lg_history(dm) # no operations yet
#> <lg_history> no operations recorded for this object yet
dm_f <- lg_filter(dm, AGE >= 18L, reason = "Minors excluded")
#> lineager: [DM] filter 'Minors excluded' — 2 in, 1 out, 1 excluded
lg_history(dm_f)
#> <lg_history> 1 operation(s)
#>
#> <lg_operation> [op_0001] FILTER
#> Dataset : DM
#> Description: Minors excluded
#> Rows : 2 -> 1 (1 excluded)
#> Timestamp : 2026-08-09T14:39:53.178Z
#>