(ns code.utils.folds (:use (code.utils utils)) (:use (incanter core)))

(defn folds1 [D nfolds]
  (let [break (Math/ceil (/ (count D) (* 1.0 nfolds)))]
    (loop [i 0 result (transient [])]
      (if (= i nfolds)
        (persistent! result)
        (recur (inc i) 
               (conj! result (if (= i 4) (sel D :rows (range (* i break) (nrow D)))
		      (sel D :rows (range (* i break) (* (inc i) break))))))))))

(defn folds [D nfolds]
  (let [nfold (folds1 D nfolds)]
    (loop [i 0 result (transient [])]
      (if (>= i nfolds)
        (persistent! result)
        (recur 
          (inc i)
          (conj! result 
                 {:index i 
                  :test (nth nfold i) 
                  :train (matrix                            
                            (apply concat (filter #(not= (nth nfold i) %) nfold)))}))))))