anchor.diff:         (apply #'make-plot :points
                     (collect-elements
                      data
  -                   :filter (lambda (e) (funcall test data-kind (funcall key e))))
  +                   :filter (lambda (e)
  +			     (funcall test data-kind (funcall key e))))
                     :x-coord x-coord
                     :y-coord y-coord
                     :plot plot
  -                  :legend (when legend-creator (funcall legend-creator data-kind))
  -                  args)
  -       (setf first? nil)))
  +                  :legend (when legend-creator
  +			    (funcall legend-creator data-kind))
  +                  args)))
       (values plot)))
   
   (defun histogram (data &rest args &key
  
positive.code:        (apply #'make-plot plot-kind
                    (collect-elements
                     data
                     :filter (lambda (e) (funcall test data-kind (funcall key e))))
                    :x-coord x-coord
                    :y-coord y-coord
                    :plot plot
                    :legend (when legend-creator (funcall legend-creator data-kind))
                    args)
         (setf first? nil)))
      (values plot)))
  
  (defun scatter-plot (data &rest args &key
  
negative.code:                           (legend-creator (lambda (x) (format nil "~A" x)))
                            &allow-other-keys)
    (remf args :key)
    (bind ((result nil)
           (plot (apply #'make-plot nil nil 
                        :title title
                        :xlabel xlabel
  