Keep only groups of data with multiple observations

Question

I am attempting to keep only deids with multiple observations.

I have the below code

help <- data.frame(deid = c(1, 5, 5, 5, 5, 5, 5, 12, 12, 12,         


        

Answer 1

Using data.table instead:

helpcount <- help[, list(Count = .N), by = deid]
helpf <- merge(help,helpcount, by = "deid")
helpf <- helpf[Count > 1]

EDIT: A bit more concise:

help[, Count := .N, by = deid]
help[Count > 1]

EDIT2: thelatemail's even more concise solution:

help[,if(.N > 1) .SD, by=deid]