Efficient functional programming (using mapply) in R for a “naturally” procedural problem

Question

A common use case in R (at least for me) is identifying observations in a data frame that have some characteristic that depends on the values in some subset of other observa

Answer 1

For the specific problem posed !rev(duplicated(rev(raw$WorkerId))) or better, following Charles' advice, !duplicated(raw$WorkerId, fromLast=TRUE)