R 仅保留具有条件的重复条目

我正在清理数据集，只需要保留重复4次的数据（如“a”和“b”），但是，我无法这样做。有人能帮忙吗

谢谢大家!

let <- c("a","a","a","a","b","b","b","b","c","c","c","d","d","e")
avg <- c(1,1,1,2,3,4,5,6,1,2,3,4,3,5)

sample <- data.frame(let,avg)

---

let我们可以使用
data.table

library(data.table)
setDT(sample)[, .SD[.N >=4], let]
#   let avg
#1:   a   1
#2:   a   1
#3:   a   1
#4:   a   2
#5:   b   3
#6:   b   4
#7:   b   5
#8:   b   6

subset(sample, let %in% names(which(rowSums(table(sample)) >=4)))


或者使用
ave

sample[with(sample, ave(avg, let, FUN = length)>=4),]

或使用
表格

library(data.table)
setDT(sample)[, .SD[.N >=4], let]
#   let avg
#1:   a   1
#2:   a   1
#3:   a   1
#4:   a   2
#5:   b   3
#6:   b   4
#7:   b   5
#8:   b   6

subset(sample, let %in% names(which(rowSums(table(sample)) >=4)))

sample%%>%group\u by（let）%%>%filter（n（）>=4）
with
dplyr