There was some discussion of an .EACHI facility for data.table. Not sure what happened about that but I have an example that might be useful:
http://stackoverflow.com/questions/24472254/splitting-a-column-by-factor-within-a-data-frame/24472571#24472571 which shows the code where DT has columns v1, v2 and v3: DT[, split(v2, v1), by = names(DT)] It works well if the rows of DT are unique but if they are not then one must do something ugly like appending a uniquifying column of 1:nrow(DT), say, and then including that in by and then finally removing it again at the end. This suggests two features: 1. The ability to tell it to do the by by row 2. The ability to selectively omit by variables from the output For example, if one could use a pseudo column .I and if -.I meant do not include it in the output then one could write: DT[, split(v2, v1), by = c(names(DT), -.I)] Other syntaxes may be thought of too and the main suggestion here is the possible need for these features rather than the specific syntax. (By the way, is there an intention to move to the issue system on github for things like this?) -- Statistics & Software Consulting GKX Group, GKX Associates Inc. tel: 1-877-GKX-GROUP email: ggrothendieck at gmail.com _______________________________________________ datatable-help mailing list [email protected] https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help
