Functional Average Height

(defn get-average-height
  [people]
  (let [people-with-height (filter #(contains? % :height) people)
        heights (map #(:height %1) people-with-height)
        total (count people-with-height)]
    (/ (reduce + heights) total)))

(defn get-average-height2
  [people]  
    (let [people-with-heights (filter #(contains? % :height) people)]
     (/ (reduce + (map #(:height %1) people-with-heights))
        (count people-with-heights))))

(get-average-height2 [{"name" "Mary" :height 160} 
                      {"name" "Isla" :height 80}
                      {"name" "Sam"}])