Diversity prediction theorem: Difference between revisions

{{trans|Clojure}}

<lang racket>#lang racket

(define (mean l)

(/ (apply + l) (length l)))

(define (diversity-theorem truth predictions)

(define μ (mean predictions))

(define (avg-sq-diff a)

(mean (map (λ (p) (sqr (- p a))) predictions)))

(hash 'average-error (avg-sq-diff truth)

'crowd-error (sqr (- truth μ))

'diversity (avg-sq-diff μ)))

(println (diversity-theorem 49 '(48 47 51)))

(println (diversity-theorem 49 '(48 47 51 42)))</lang>

<pre>'#hash((average-error . 3) (crowd-error . 1/9) (diversity . 2 8/9))

'#hash((average-error . 14 1/2) (crowd-error . 4) (diversity . 10 1/2))</pre>