gistfile1.clj

(defn car-model
  [year engine kind]
  (str year "/" (format "%.1f" (float (read-string engine))) "/" (clojure.string/capitalize kind)))

(defn group-car-data-by-model
  [car-data]
  (reduce (fn [results row]
              (let [[year reg engine mileage price kind] row
                    model (car-model year engine kind)
                    cars (get-in results [model] [])]
                (assoc-in results [model] (conj cars {:mileage mileage
                                                      :price price})))) {} car-data))

(defn get-grouped-car-data
  [in-path]
  (with-open [in-file (io/reader in-path)]
    (group-car-data-by-model (csv/read-csv in-file))))

(keys (get-grouped-car-data (project-path "mx5.csv")))
; ("2011/1.8/Convertible" "2012/1.8/Convertible" "2008/2.0/Convertible" "2008/1.8/Coupe" "2009/1.8/Coupe" "2009/2.0/Convertible" "2006/1.8/Convertible" "2008/1.8/Convertible" "2009/1.8/Convertible" "2010/2.0/Coupe" "2011/2.0/Coupe" "2010/1.8/Coupe" "2010/2.0/Convertible" "2011/2.0/Convertible" "2011/1.8/Coupe" "2012/1.8/Coupe" "2008/2.0/Coupe" "2009/2.0/Coupe" "2010/1.8/Convertible")