How to select the 10% of highest and lowest values from a vector in R?

Question

As introduce in the title, I would like to select the 10% highest and the 10% lowest values from a vector. How can I manage to do that?

Anyone can help me ? Thanks a lot

Answer 1

This is an example that takes roughly 10%:

v <- rnorm(100)
sort(v)[1:(length(v)/10)]                  # lowest, in increasing order.
sort(v, decreasing=TRUE)[1:(length(v)/10)] # highest, in decreasing order.

Answer 2

This will return a vector containing the bottom and top 10% of x:

> set.seed(123)
> x<-rnorm(100)
> x[{q<-rank(x)/length(x);q<0.1 | q>=0.9}]
 [1]  1.558708  1.715065 -1.265061  1.786913 -1.966617 -1.686693 -1.138137
 [8]  1.253815 -1.265396  2.168956 -1.123109  1.368602  1.516471 -1.548753
[15]  2.050085 -2.309169 -1.220718  1.360652  2.187333  1.532611