How to delete a row by reference in data.table?

Question

My question is related to assignment by reference versus copying in data.table. I want to know if one can delete rows by reference, similar to

Answer 1

The topic is still interesting many people (me included).

What about that? I used assign to replace the glovalenv and the code described previously. It would be better to capture the original environment but at least in globalenv it is memory efficient and acts like a change by ref.

delete <- function(DT, del.idxs) 
{ 
  varname = deparse(substitute(DT))

  keep.idxs <- setdiff(DT[, .I], del.idxs)
  cols = names(DT);
  DT.subset <- data.table(DT[[1]][keep.idxs])
  setnames(DT.subset, cols[1])

  for (col in cols[2:length(cols)]) 
  {
    DT.subset[, (col) := DT[[col]][keep.idxs]]
    DT[, (col) := NULL];  # delete
  }

  assign(varname, DT.subset, envir = globalenv())
  return(invisible())
}

DT = data.table(x = rep(c("a", "b", "c"), each = 3), y = c(1, 3, 6), v = 1:9)
delete(DT, 3)