anchor.diff:            do (setf (dtree-id dtree) i))
       ;; set leaf-id
       (set-leaf-index-forest! forest)
  +    (setf (forest-n-leaf forest)
  +          (apply #'+ (mapcar #'dtree-max-leaf-index
  +                             (forest-dtree-list forest))))
       forest))
   
   (defun make-regression-forest (datamatrix target
  
positive.code:              (let* ((leaf (find-leaf (dtree-root dtree) datamatrix i))
                      (leaf-index (node-leaf-index leaf))
                      (leaf-mean (node-regression-mean leaf))
                      (destination-index (car (svref refine-dataset i)))
                      (destination-value (cdr (svref refine-dataset i))))
                 ;; (declare (type fixnum leaf-index)
                 ;;          (type (simple-array fixnum) destination))
                 (setf (aref destination-index tree-id) (+ leaf-index offset))
                 (setf (aref destination-value tree-id) leaf-mean)))))
         (forest-dtree-list forest))
        refine-dataset)))
  
  
negative.code:           do (setf (dtree-id dtree) i))
      ;; set leaf-id
      (set-leaf-index-forest! forest)
      (setf (forest-n-leaf forest)
            (apply #'+ (mapcar #'dtree-max-leaf-index
                               (forest-dtree-list forest))))
      forest))
  
  (defun class-distribution-forest (forest datamatrix datum-index)
  