topn: Highest elements in a vector.
In traversc/trqwe: Performance oriented statistical metrics and utility functions.

Description Usage Arguments Value See Also Examples

Finds the top elements in a vector very quickly. Equivalent ot -sort(-x, partial=1:n)

1	topn(x, n = 100, value = F, lowest = F)

`x`	A numeric vector.
`n`	The number of top elements to return.
`value`	If TRUE, returns the values of the top elements. If FALSE, returns the indices.
`lowest`	If TRUE, returns the lowest elements instead of the highest.

A vector containing the indices or the values of the top elements.

http://stackoverflow.com/questions/18450778/

naive_top <- function(x, n) {
   -sort(-x, partial=1:n)
}
x <- runif(1e7)
microbenchmark(naive_top(x,100), topn(x,100,value=T), times=10)

Unit: milliseconds
                   expr       min        lq     mean    median        uq
      naive_top(x, 100) 1070.0180 1071.5951 1075.964 1072.3520 1073.9989
topn(x, 100, value = T)  433.6682  433.8882  434.771  434.4986  435.6029