R Left Outer Join with 0 Fill Instead of NA While Preserving Valid NA's in Left Table

Question

What is the easiest way to do a left outer join on two data tables (dt1, dt2) with the fill value being 0 (or some other value) instead of NA (default) without overwriting valid

Answer 1

I stumbled on the same problem with dplyr and wrote a small function that solved my problem. (the solution requires tidyr and dplyr)

left_join0 <- function(x, y, fill = 0L){
  z <- left_join(x, y)
  tmp <- setdiff(names(z), names(x))
  z <- replace_na(z, setNames(as.list(rep(fill, length(tmp))), tmp))
  z
}