percentiles.clj

(defn percentiles [xs]
  (let [sorted (sort xs)
        how-many (count sorted)
        percentile (fn [n]
                     (let [idx (Math/floor (* how-many (/ n 100)) )]
                       (nth sorted idx)))]
    {:mean (mean xs)
     :median (percentile 50)
     :90 (percentile 90)
     :95 (percentile 95)
     :99 (percentile 99)}))