R: data.table cross-join not working

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There is no cross join functionality available in data.table out of the box.
Yet there is CJ.dt function (a CJ like but designed for data.tables) to achieve cartesian product (cross join) available in optiRum package (available in CRAN).
You can create the function:

CJ.dt = function(X,Y) {
  stopifnot(is.data.table(X),is.data.table(Y))
  k = NULL
  X = X[, c(k=1, .SD)]
  setkey(X, k)
  Y = Y[, c(k=1, .SD)]
  setkey(Y, NULL)
  X[Y, allow.cartesian=TRUE][, k := NULL][]
}
CJ.dt(dtCustomers, dtDates1)
CJ.dt(dtCustomers, dtDates2)

Yet there is a FR for convenience way to perform cross join filled in data.table#1717, so you could check there if there is a nicer api for cross join.

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