anchor.diff:    
     (values plot))
   
  -;;; ---------------------------------------------------------------------------
  -
   (defmethod make-data-set (plot-kind data
                             &rest args
                             &key (comment nil)
  
positive.code:     :host *plot-default-host*
      :directory *plot-default-directory*)
    (:export-slots filename))
  
  ;;; ---------------------------------------------------------------------------
  
  (defclass* plot-data-set ()
    ((settings (make-container 'simple-associative-container) r)
  
negative.code: 		       (format-value-for-gnuplot name value))
  	       (setf first? nil)))))))))
  
  (defmethod write-data-set ((data-set plot-data-set) out)
    (iterate-elements
     (data data-set)
     (lambda (datum)
       (format out "~{~A ~}~C" datum #\Linefeed)))
    (format out "e~C" #\Linefeed))
  
  (defmethod make-plot ((plot-kind symbol) data 
                        &rest args
  