If your vector contains only integers, tabulate will be much faster than anything else. There are a couple of catches to be aware of:
- It'll by default return the count for numbers from 1 to N.
- It'll return an unnamed vector.
That means, if your x = c(1,1,1,3) then tabulate(x) will return (3, 0, 1). Note that the counts are for 1 to max(x) by default.
How can you use tabulate to make sure that you can pass any numbers?
set.seed(45)
x <- sample(-5:5, 25, TRUE)
# [1] 1 -2 -3 -1 -2 -2 -3 1 -3 -5 -1 4 -2 0 -1 -1 5 -4 -1 -3 -4 -2 1 2 4
Just add abs(min(x))+1 when min(x) <= 0 to make sure that the values start from 1. If min(x) > 0, then just use tabulate directly.
sort(setNames(tabulate(x + ifelse(min(x) <= 0, abs(min(x))+1, 0)),
seq(min(x), max(x))), decreasing=TRUE)[1:3]
If your vector does contain NA, then you can use table with useNA="always" parameter.
