Clojure从zipmap获得最高值

Question

因此，我在这里得到了我建议的邮政编码地图，它工作得很好。如你所见，我已经加载了数据。

这就是它在repl中的样子，这是完美的。这就是地图

:Year 2020, :Day 27, :January 59, :February 38
:Year 2020, :Day 28, :January 41, :February 57
:Year 2020, :Day 29, :January 56, :February 51
:Year 2020, :Day 31, :January 94, :February -999
:Year 2020, :Day 30, :January 76, :February -999 

(map [:Day :Month

请记住，这只是我所做的代码片段。你会怎么建议我在一月份找到最高价值的一天？我说的最高数字是指紧挨着月份的数字

(into(sorted-map-by >(fn [:January]))Ha) 

我尝试了一下，但没有成功，末尾的"Ha“就是我初始化zipmap并使用io/ read读取文件的函数的名称

Answer 1

我会使用max-key和reduce

(def data [{:Year 2020, :Day 27, :January 59, :February 38}
           {:Year 2020, :Day 28, :January 41, :February 57}
           {:Year 2020, :Day 29, :January 56, :February 51}
           {:Year 2020, :Day 31, :January 94, :February -999}
           {:Year 2020, :Day 30, :January 76, :February -999}])

(reduce (partial max-key :January) data)
;; => {:Year 2020, :Day 31, :January 94, :February -999}

(:Day (reduce (partial max-key :January) data))
;; => 31

Answer 2

不确定你的确切数据结构是什么样子，但假设它是一个地图矢量，你可以这样做：

(def data
  [{:Year 2020, :Day 27, :January 59, :February 38}
   {:Year 2020, :Day 28, :January 41, :February 57}
   {:Year 2020, :Day 29, :January 56, :February 51}
   {:Year 2020, :Day 31, :January 94, :February -999}
   {:Year 2020, :Day 30, :January 76, :February -999}])

(->> data
     (sort-by :January)
     last
     :January)
;; => 94

通过使用关键字作为函数对向量进行排序以在映射中查找它的值，然后获取具有一月最高值的向量，然后从该向量中获得属于关键字:January的值。如果您的数据结构看起来有点不同，请告诉我。

Answer 3

@Rulle的答案非常好。如果没有max-key，它将是：

(def data [{:Year 2020, :Day 27, :January 59, :February 38}
           {:Year 2020, :Day 28, :January 41, :February 57}
           {:Year 2020, :Day 29, :January 56, :February 51}
           {:Year 2020, :Day 31, :January 94, :February -999}
           {:Year 2020, :Day 30, :January 76, :February -999}])

(defn seq-max [seq greater key]
  (reduce (fn [a b] (if (greater (key a) (key b)) a b)) seq))
;; if no key is wanted, choose the function `identity` as key!
;; e.g.
;; (seq-max (map :January data) > identity)
;; => 94

(:Day (seq-max data > :January)) ;; => 31