Cumulative number of unique values in a column up to current row

Question

I have a data frame, donorInfo, with donor information:

id        giftdate     giftamt
002       2001-01-05     25.00
033       2001-05-08     5         


        

Answer 1

try something like this:

donorInfo$numUnique<-sapply(seq(nrow(donorInfo)), function(rn){
  length(unique(donorInfo$id[seq(rn)]))
})

Not the most efficient solution no doubt, but it should work.