Вы можете использовать dplyr
:
result<-quiz%>%
group_by(circleid)%>%
summarise_all(n_distinct)
microbenchmark
для data.table
и dplyr
:
microbenchmark(x1=quiz[, lapply(.SD, function(x) length(unique(x))), by = circleid],
x2=quiz%>%
group_by(circleid)%>%
summarise_all(n_distinct),times=100)
Unit: milliseconds
expr min lq mean median uq max neval cld
x1 150.06392 155.02227 158.75775 156.49328 158.38887 224.22590 100 b
x2 41.07139 41.90953 42.95186 42.54135 43.97387 49.91495 100 a