Univariate stats example: as 'let'

univariate_stats.clj

;; Take a map {:xs xs} and return a map
;; of simple univariate statistics of xs
(defn stats [{:keys [xs]}]
  (let [n  (count xs)
        m  (/ (sum identity xs) n)
        m2 (/ (sum #(* % %) xs) n) 
        v  (- m2 (* m m))]
    {:n n   ; count   
     :m m   ; mean 
     :m2 m2 ; mean square
     :v v   ; variance
    }))

(stats {:xs [1 2 3 6]})
; ==> {:n 4     
;      :m 3 
;      :m2 12.5 
;      :v 3.5)