Add multiple columns to R data.table in one function call?

by

Since data.table v1.8.3, you can do this:

DT[, c("new1","new2") := myfun(y,v)]

Another option is storing the output of the function and adding the columns one-by-one:

z <- myfun(DT$y,DT$v)
head(DT[,new1:=z$r1][,new2:=z$r2])
#      x y  v new1 new2
# [1,] a 1 42   43  -41
# [2,] a 3 42   45  -39
# [3,] a 6 42   48  -36
# [4,] b 1  4    5   -3
# [5,] b 3  5    8   -2
# [6,] b 6  6   12    0

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