All, Is there some data.table-idiomatic way to filter based on a previous observation/row? For example, I want to remove a row if DT$a[row]==DT$a[row-1].
It could be done by first calculating the lag and then filtering based on that, but I wonder if there's a more direct way. The following example works, but my feeling is there should be a more elegant solution: ( DT <- data.table(a = c(1, 2, 2, 3), b = 8:5) ) DT[, L.a := c(NA, head(a, -1))][a != L.a | is.na(L.a)][, L.a := NULL][] Thanks, M _______________________________________________ datatable-help mailing list [email protected] https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help
