timezone-visualization.rkt

#lang racket
(require json)

(define filename "combined.json")

(define timezone-data (call-with-input-file filename read-json))

(define (random-sample object [max-size 5])
  (cond
   ((hash? object)
    (for/hash ([(k v) (in-hash object)])
      (values k (random-sample v max-size))))
   ((list? object)
    (let ([len (length object)])
      (if (> len max-size)
          (let ([samples (sort (build-list max-size (lambda (x) (random len))) <)])
            (for/list ([(x position) (in-indexed (in-list object))]
                       #:when (member position samples))
              (random-sample x max-size)))
          (for/list ([x (in-list object)])
            (random-sample x max-size)))))
   (#t object)))


(random-sample timezone-data 2)