[datatable-help] In R data.table, how do I pass variable parameters to an expression?

[Jitender]

I am stuck with a small R issue with data.table. Your help is much
appreciated. How do I do this:

get <- function(dt, expr, gby) {
  e <- substitute(expr)
  b <- substitute(gby)
  return(dt[,eval(e),by=b])
}

v1 <- "Sepal.Length"
v2 <- "Species"

dt <- data.table(iris)
rDT <- get(dt, sum(v1, na.rm=TRUE), v2)

I get following error: Error in sum(v1, na.rm = TRUE) : invalid 'type'
(character) of argument

Now, both v1 and v2 get passed from other program as character variable so
I can't do this v1<- quote(Sepal.Length) which seems to work.
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