Why can't one have several `value.var` in `dcast`?

Question

Why can\'t one have multiple variables passed to value.var in dcast? From ?dcast:

value.var name of column whi

Answer 1

Try coercing your data.frame into a data.table using setDT or as.data.table.

dcast(setDT(C93L), AirBags ~ DriveTrain , mean, value.var=c("Price","Weight"))