5

嗨 huys：我想为地图中的所有值绘制一个“平均值”。说我有一张地图清单：

[{"age" 2 "height" 1 "weight" 10},
{"age" 4 "height" 4 "weight" 20},
{"age" 7 "height" 11 "weight" 40}]

我想要的输出是

{"age 5 "height" 5 ....}

///下面是我脑子里乱七八糟的东西，即我想象的在 Clojure 中工作的方式......不要太认真

转置列表：

  {"age" [2 4 7] "height" [1 4 11] }

然后我可以简单地做类似的事情（再次，在这里组成一个名为 freduce 的函数）

  (freduce average (vals (map key-join list)))

要得到

{"age" 5 "weight" 10 "height" 7}

4

6 回答 6

6

创建向量图：

（减少（fn [m [kv]]
          (assoc mk (conj (get mk []) v)))
        {}
        （应用 concat list-of-maps））

创建平均值图：

（减少（fn [m [kv]]
          (assoc mk (/ (reduce + v) (count v))))
        {}
        向量图）
于 2011-10-23T08:58:12.210 回答
5

看看合并

这是我的一些实际代码：

(let [maps [{"age" 2 "height" 1 "weight" 10},
            {"age" 4 "height" 4 "weight" 20},
            {"age" 7 "height" 11 "weight" 40}]]
  (->> (apply merge-with #(conj %1 %2)
             (zipmap (apply clojure.set/union (map keys maps))
                     (repeat [])) ; set the accumulator
             maps)
       (map (fn [[k v]] [k (/ (reduce + v) (count v))]))
       (into {})))
于 2011-10-23T05:34:55.947 回答
4

这是一个相当冗长的解决方案。希望有人能想出更好的东西：

(let [maps [{"age" 2 "height" 1 "weight" 10},
            {"age" 4 "height" 4 "weight" 20},
            {"age" 7 "height" 11 "weight" 40}]
      ks (keys (first maps))
      series-size (count maps)
      avgs (for [k ks]
             (/ (reduce +
                        (for [m maps]
                          (get m k)))
                series-size))]
  (zipmap ks avgs))
于 2011-10-23T06:07:24.597 回答
2 
(defn key-join [map-list]
  (let [keys (keys (first map-list))]
       (into {} (for [k keys] [k (map #(% k) map-list)]))))
(defn mapf [f map]
  (into {} (for [[k v] map ] [k (f v)])))
(defn average [col]
  (let [n (count col)
        sum (apply + col)]
       (/ sum n)))

演示

user=> (def data-list [{"age" 2 "height" 1 "weight" 10},
{"age" 4 "height" 4 "weight" 20},
{"age" 7 "height" 11 "weight" 40}])
#'user/data-list
user=> (key-join data-list)
{"age" (2 4 7), "height" (1 4 11), "weight" (10 20 40)}
user=> (mapf average (key-join data-list))
{"age" 13/3, "height" 16/3, "weight" 70/3}
于 2011-10-23T11:11:21.127 回答
1

这是另一个使用没有 zipmap 的合并的版本。

(let [data [{:a 1 :b 2} {:a 2 :b 4} {:a 4 :b 8}]
           num-vals (count data)]
     (->> data (apply merge-with +) 
          (reduce (fn [m [k v]] (assoc m k (/ v num-vals))) {})))
于 2011-10-23T10:40:36.880 回答
1

这是我的单线解决方案：

(def d [{"age" 2 "height" 1 "weight" 10},
   {"age" 4 "height" 4 "weight" 20},
   {"age" 7 "height" 11 "weight" 40}])

(into {} (map (fn [[k v] [k (/ v (count d))]]) (apply merge-with + d)))

=> {"height" 16/3, "weight" 70/3, "age" 13/3}

逻辑如下：

  • 在地图上使用 merge-with + 来计算每个键值的总和
  • 将所有结果值除以地图总数以获得平均值
  • 将结果放回带有 (into {} ...) 的哈希图中
于 2011-11-24T16:28:06.677 回答