I have a vector and I'm able to return highest and lowest value, but how to return 5 topmost values? Is there a simple one-line solution for this?
> a <- c(1:100)
> tail(sort(a),5)
[1] 96 97 98 99 100
x[order(x)[1:5]]
Yes, head( X, 5) where X is your sorted vector.
tail(sort.int(x, partial=length(x) - 4), 5)
Using sort.int with partial has the advantage of being (potentially) faster by (potentially) not doing a full sort. But in reality, my implementation appears a little slower. Maybe this is because with parameter partial != NULL, shell sort is used rather than quick sort?
> x <- 1:1e6
> system.time(replicate(100, tail(sort.int(x, partial=length(x) - 4), 5)))
user system elapsed
4.782 0.846 5.668
> system.time(replicate(100, tail(sort(x), 5)))
user system elapsed
3.643 0.879 4.854
来源：https://stackoverflow.com/questions/3692563/how-to-return-5-topmost-values-from-vector-in-r