Converters for Resampling <-> data.table

[mllg]

No description provided.

[jemus42]

Observations from implementing this for my use case where the as.data.table(Resampling) is stored as CSV:

• I needed to ensure the dt is keyed appropriately (data.table::fread(..., key = c("set", "iteration"))) for the join(?) to work (x[list("train"), list(ids = list(row_id)), by = "iteration"]$ids), to avoid a warning. Maybe asserting keys is useful?
• assert_factor(x$set, any.missing = FALSE) might be a little strict, given that it should suffice for set to be a character and assert_set_equal(unique(x$set), c("train", "test"))? When taking the detour to a CSV file set could end up being either character or factor I guess.

[berndbischl]

@mllg can you please describe what this supposed does or solve?

[berndbischl]

i mean, i can see what happens in the code. i think this is good, if we test and doc this well

[berndbischl]

i would add a small feature like this:
a) if we go from a Resample (instantiated) to a table, this is easy.
b) if we read from a table, we go to a ResamplingCustom (if the user gives no extra type)
and we perform some very basic validity checks
c) if the user provides the type (we should at least for now support HO, subsamp, CV, rep-CV) we convert into that type (not custom) and perform a few more validity checks