Repository navigation
Allow type override in := when i is just order() #2925
Description
DT = data.table(a = 1:10)
DT[order(-a), a := paste0(a)]
This errors saying we should be explicit about type overrides, but:
DT[ , a := paste0(a)]
This code works fine (and is of course identical, but the same problem arises when the column update is order-dependent). Presumably this is because when i is non-empty, := suspects there could be a type collision if assigning a new type to a subset of rows.
But order queries in i are incapable of subsetting, so I would expect the behavior to be identical.
Activity
MichaelChirico commentedon Oct 7, 2021
I got bit by this again.
Here seems like perfectly reasonable code to me:
Now, try to convert
ato factor, with levels generated in reverse-border:Actually, nothing is done -- because
ais acharacter, and we're trying to assignfactor->character,["smartly" coerces factor->character, resulting in no change at all (PS this is not at all clear from the verbose output, which could be improved -- I was totally at sea until I tried an example whereastarts out asinteger, then the:=fails because it tries to assigninteger->character, an error).As a workaround I'm basically forced to create a placeholder variable like
a_factoror something like thatMichaelChirico commentedon Sep 5, 2024
IINM one workaround is to use
sort_by()for now: