(defn $group-by
"Returns a map of datasets keyed by a query-map corresponding the group.
Examples:
(use '(incanter core datasets))
($group-by :Species (get-dataset :iris))
($group-by [:hair :eye] (get-dataset :hair-eye-color))
(with-data (get-dataset :hair-eye-color)
($group-by [:hair :eye]))
"
([cols]
($group-by cols $data))
([cols data]
(let [n (nrow data)
rows (:rows data)]
(loop [r 0 grouped-rows {}]
(if (= r n)
(let [group-cols (keys grouped-rows)
res (apply assoc {} (interleave group-cols (map to-dataset (vals grouped-rows))))]
res)
(recur (inc r)
(let [row (nth rows r)
k (submap row cols)
k-rows (grouped-rows k)]
(assoc grouped-rows k (if k-rows (conj k-rows row) [row])))))))))
Used in 0 other vars
Source
incanter/core.clj:1803
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