可以用 2 个键和 Clojure 中的值向量创建一个 map 吗？

Question

I am trying to create a program that reads in a table of temperatures from a csv file and would like to access aa collection of temperatures based on the year and day.

the first column stands for the year the tempratures have been recorded. the second column stands for a specific day during each month. the rest of the column represent the temperatures each month.

For example, 2021 - 23 - 119 = 23rd June 2021 has a temperature of 119

Year   Day      Months from January to December

2018     18  | 45   54  -11  170   99  166  173  177  175   93   74   69

2021     23  | 13   87   75   85   85  119  190  172  156  104   39   53 


2020     23  | 63   86   62  128  131  187  163  162  138  104   60   70 

So far I have managed to load the data from a CSV File with clojure.data.csv . this returns a sequence of vectors into the program

  (defn Load_csv_file  [filepath]
 (try
   (with-open [reader (io/reader filepath)]
     (.skip reader 1)
     ( let [data (csv/read-csv reader)]
       (println  data) )
     )
   (catch Exception ex (println (str "LOL Exception: " (.toString ex))))
   ))

I am currently trying to figure out how to implement this but my reasoning was to create three keys in a map which will take in the year, day and vector of temperatures, to then filter for a specific value.

Any advice on how i can implement this functionality.

Thanks!

Answer 1

i would go with something like this:

(require '[clojure.java.io :refer [reader]]
         '[clojure.string :refer [split blank?]]
         '[clojure.edn :as edn])

(with-open [r (reader "data.txt")]
  (doall (for [ln (rest (line-seq r))
               :when (not (blank? ln))
               :let [[y d & ms] (mapv edn/read-string (split ln #"\s+\|?\s+"))]]
           {:year y :day d :months (vec ms)})))

;;({:year 2018,
;;  :day 18,
;;  :months [45 54 -11 170 99 166 173 177 175 93 74 69]}
;; {:year 2021,
;;  :day 23,
;;  :months [13 87 75 85 85 119 190 172 156 104 39 53]}
;; {:year 2020,
;;  :day 23,
;;  :months [63 86 62 128 131 187 163 162 138 104 60 70]})

by the way, i'm not sure csv format allows different separators (as you have in your example.. anyway this one would work for that)

Answer 2

I would create a map of data that looked something like this

{2020 {23 {:months [63 86 62 128 131 187 163 162 138 104 60 70]}}}

This way you can get the data out in a fairly easy way (get-in data [2020 23:months]

So something like this

(->> (Load_csv_file "file.csv")
     (reduce (fn [acc [year day & months]] (assoc-in acc [year day] months)) {}))

This will result in the data structure I mentioned now you just need to figure out the location of the data you want