The documentation says that all variables serving as keys in a data table must be of storage mode integer, so the short answer to your question is yes. Integers and factors are 'naturally' of storage mode factor in R, character variables assigned as keys are coerced to factor so that they have storage mode integer and numeric variables assigned as keys are coerced to integer for the same reason. I believe the reason for this (which is explained in the vignette and FAQ, if memory serves) is to make binary search as efficient as possible.
HTH, Dennis -- View this message in context: http://r.789695.n4.nabble.com/Does-setkey-silently-coerce-numeric-to-integer-tp2969728p2970678.html Sent from the datatable-help mailing list archive at Nabble.com. _______________________________________________ datatable-help mailing list [email protected] https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help
