figure2-1.rkt

(require plot)
(plot-font-size 24)
(plot-height 800)
(plot-width 800)
(define f (λ (x) (+ (* 3 x) 2 )))
(define xs (range -30 30 0.1))
(define ys (map
  (lambda (x)
    (+
      (f x)
      (- (* 40 (random)) 20)
    )
  )
  xs
))
(plot
  (list
    (function (λ (x) (+ (* 3 x) 2 )) -30 30 #:label "f(x) = 3 * x + 2")
    (points (map vector xs ys) #:sym 'dot #:size 10 #:label "f(x) +/- 20 * random")
  )
  #:x-label ""
  #:y-label ""
)