Clojure for Data Science

Parse the data

Since the data will all fit in the main memory for convenience, we'll define several functions that will load the ratings into Clojure data structures. The line->rating function takes a line, splits it into fields where a tab character is found, converts each field to a long datatype, then uses zipmap to convert the sequence into a map with the supplied keys:

(defn to-long [s]
  (Long/parseLong s))

(defn line->rating [line]
  (->> (s/split line #"\t")
       (map to-long)
       (zipmap [:user :item :rating])))

(defn load-ratings [file]
  (with-open [rdr (io/reader (io/resource file))]
    (->> (line-seq rdr)
         (map line->rating)
         (into []))))

(defn ex-7-3 []
  (->> (load-ratings "ua.base")
       (first)))

;; {:rating 5, :item 1, :user 1}

Let's write a function to ...