How to get the top n elements (in terms of frequency) from a vector in R?

Question

How can I get the top n ranking of an array in R?

lets say I have

a <- c(67, 2, 100, 2, 100, 23, 2, 100, 67, 89,100)

how can I get:

rank   number   times
1     100       4
2     2         3
3     67        2
4     23        1
4     89        1

Answer 1

tab <- table(a<-c(67, 2, 100, 2, 100, 23, 2, 100, 67, 89,100))
df <- as.data.frame(tab)
names(df) <- c("number","times")
df$rank <- rank(-df$times,ties.method="min")
df <- df[order(df$rank,decreasing = F),]
df
  number times rank
5    100     4    1
1      2     3    2
3     67     2    3
2     23     1    4
4     89     1    4