r - Combining vector and binary search in data.table -


sometimes, have keyed data.table i'd subset according key and unkeyed column. what's simplest/fastest way this?

what feels natural error:

dt <- data.table(id = 1:100, var = rnorm(100), key = "id") dt[.(seq(1, 100, 2)) & var > 0, ]

the next cleanest thing chain:

dt[.(seq(1, 100, 2))][var > 0, ]

and of course can ditch using binary search @ (i think avoided):

dt[id %in% seq(1, 100, 2) & var > 0, ]

is there approach i'm missing? also, particular reason why first error? syntax seems clear enough me.

as of writing, native way do:

dt[.(seq(1, 100, 2)) & var > 0, j] #some expression j

is following:

dt[.(seq(1, 100, 2)), .sd[var > 0, j]]

the more work data.table, more natural is, still looks bit unintuitive. c'est la vie.


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