Thank you, I did not even think of wrapping in ( ) for the ':=" scenario. Feeling a bit silly about that.
Just fooling around I did discover that dt[, "new.var" := fun(var), by = something] does work. For some reason I had been wrapping that (go figure), i.e. dt[, .("new.var" := fun(var)), by = something] and that just gave error messages. Two ways to do it and I choose the wrong one both times. Sincerely appreciate the help Carl Sutton ----- Carl Sutton -- View this message in context: http://r.789695.n4.nabble.com/and-throwing-errors-tp4718825p4719212.html Sent from the datatable-help mailing list archive at Nabble.com. _______________________________________________ datatable-help mailing list datatable-help@lists.r-forge.r-project.org https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help