(defun median (v1 v2)
  (let ((vhat))
    (dotimes (i (length v1))
      (if (numberp (nth i v1))
	  (push (/ (+ (nth i v1) (nth i v2)) 2) vhat)
	  (if (eql (nth i v1) (nth i v2))
	      (push (nth i v1) vhat)
	      (push (random-element (list (nth i v1) (nth i v2))) vhat))))
    (reverse vhat)))

;(defun median (v1 v2)
;  (let ((vhat))
;    (dotimes (i (length v1))
;      (if (eql (nth i v1) (nth i v2))
;	  (push (nth i v1) vhat)
;	  (push (random-element (list (nth i v1) (nth i v2))) vhat)))
;    (reverse vhat)))


(defun favored-median-num (v1 v2 &optional (w1 1) (w2 1))
  "v1 is weighted more than v2 in the median"
  (let ((vhat))
    (dotimes (i (length v1))
      (let (l)
	(dotimes (j (1+ w1))
	  (push (nth i v1) l))
	(dotimes (k (1+ w2))
	  (push (nth i v2) l))
	(if (numberp (nth i v1))
	    (push (/ (sum l) (length l)) vhat)
	    (if (eql (nth i v1) (nth i v2))
		(push (nth i v1) vhat)
		(push (random-element l) vhat)))))
    (reverse vhat)))

(defun favored-median (v1 v2 &optional (w1 1) (w2 1))
  "v1 is weighted more than v2 in the median"
  (let ((vhat))
    (dotimes (i (length v1))
      (let (l)
	(dotimes (j (1+ w1))
	  (push (nth i v1) l))
	(dotimes (k (1+ w2))
	  (push (nth i v2) l))
	(if (eql (nth i v1) (nth i v2))
	    (push (nth i v1) vhat)
	    (push (random-element l) vhat))))
    (reverse vhat)))

(deftest test-median ()
  "Return a median of the values in a table"
  (let ((egsx (mapcar #'eg-features (egs (weather-numerics)))))
    (median (random-element egsx)
	    (random-element egsx))))

(defun sum (l)
  (let ((s 0))
    (dolist (v l)
      (setf s (+ s v)))
    s))