anchor.diff:      (print result)
       (/ (- result) (1+ rowNum))))
   
  +#|
   (defun compute-cost-2 (X theta y)
     (let ((result 0))
       (dotimes (r (elt (array-dimensions X) 0)
  
positive.code:     ))
  
  
  ;;; exercise below
  
  (defvar *X*)
  (setf *X*
        (let ((temp
  
negative.code:                             (log (logistic-regression (array-multiply (array-slice X r) theta))))
                           (* (- 1 (nth r y))
                              (log (- 1 (logistic-regression (array-multiply (array-slice X r) theta)))))))))
      ))|#
  
  (defun partial-derivative-lr (X theta y)
    "X is a r*c matrix"
  