topN: Average value of the top elements in each row of a matrix.

In DominikMueller64/dmisc: Dominik Mueller's R Code

Description

Takes a matrix and computes the arithmetic mean of the top elemens for each single row.

Usage

topN(x, nth)

Arguments

x	a numeric matrix
nth	an integer giving the desired number of top elemens

Value

A numeric vector containing the respective means of the top nth elements in each row.

Author(s)

Dominik Mueller

Examples

(x <- apply(matrix(seq_len(16), ncol = 4), 2L, sample))
topN(x, 2L)

# benchmarking with a pure R solution
x <- matrix(rnorm(1000L ^ 2L), ncol = 1000L)
microbenchmark::microbenchmark(times = 1L,
  a <- apply(x, 1L, function(x) mean(head(sort(x, decreasing = TRUE), 20L))),
  b <- topN(x, 20L)
)
all(dplyr::near(a, b))

DominikMueller64/dmisc documentation built on May 6, 2019, 2:52 p.m.