R/topk.R

In j1wan/topk: min/max/argmin/argmax k elements

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WhichMinK <- function(x, k) {
  c <- sort(x, partial = k)[k]
  idx <- which(x <= c)
  return(idx[order(x[idx])])
}


WhichMaxK <- function(x, k) {
  n <- length(x)
  m <- n - k
  c <- sort(x, partial = m)[m]
  idx <- which(x > c)
  return(idx[order(x[idx], decreasing = T)])
}


MinK <- function(x, k) {
  return(x[WhichMinK(x, k)])
}


MaxK <- function(x, k) {
  return(x[WhichMaxK(x, k)])
}