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[Request] Allow rbindlist(L, idcol = v) for any vector v of matching length #2159
Description
I have a list of tables (read from disk) that I want to stack with rbindlist, assigning an id column:
library(data.table)
DT = data.table(f_id = 2:3, tab = list(
data.table(g = 1:2, v = (1:2)*10),
data.table(g = 3:4, v = (3:4)*10)
))
tabDT = DT[, rbindlist(setNames(tab, f_id), idcol = "f_id")][, f_id := as.integer(f_id) ][]
Because my id column is not a character, I need to type it four (!) times and manually coerce it back to the correct class. There are other ways to handle it, but all the ones I can think of are quite clunky, like...
tabDT = DT[, rbindlist(tab, idcol = TRUE)][, `:=`(f_id = DT$f_id[.id], .id = NULL)][]
So I'd like syntax like this instead:
DT[, rbindlist(tab, idcol = f_id, idcol.name = "f_id")]
# or
DT[, rbindlist(tab, idcol = list(f_id = f_id))]
# or
DT[, rbindlist(tab, idcol = f_id)]
# with the name automatically inferred in the last case
Activity
MichaelChirico commentedon May 10, 2017
Agree with this. I swore I had already put up this FR in fact!
arunsrinivasan commentedon Jun 29, 2017
This'd be better implemented with a separate function like
unwrap(), for example. I remember having an implementation somewhere.. will have to check old local branches..arunsrinivasan commentedon Jun 29, 2017
Marking this as a dup of #2146. If you feel strongly that
rbindlistis the way to go, feel free to reopen and give your thoughts.franknarf1 commentedon Jun 29, 2017
That sounds good. I could get used to a
unnest(DT[, c("f_id", "tab")], id = "f_id")idiom or whatever. (I'm not familiar with unnest syntax and always keep a single column for an ID.)