data-science-from-scratch-2-singkong.txt

#
Data Science from Scratch
Second Edition
(First Principles with Python)
By: Joel Grus (O'Reilly)
Copyright 2019 Joel Grus
ISBN: 978-1-492-04113-9

Translated to Singkong Programming Language
(c) Noprianto <nopri.anto@icloud.com>
Free to use and/or redistribute
https://nopri.github.io/singkong.html
;

load_module("util")

var sep = "-" * 60 
var nl = newline()

#page 3-5;
println("Page 3 - 5", sep)
var users = [
    {"id": 0, "name": "Hero"},
    {"id": 1, "name": "Dunn"},
    {"id": 2, "name": "Sue"},
    {"id": 3, "name": "Chi"},
    {"id": 4, "name": "Thor"},
    {"id": 5, "name": "Clive"},
    {"id": 6, "name": "Hicks"},
    {"id": 7, "name": "Devin"},
    {"id": 8, "name": "Kate"},
    {"id": 9, "name": "Klein"}
]

var friendship_pairs = [
    [0, 1],
    [0, 2],
    [1, 2],
    [1, 3],
    [2, 3],
    [3, 4],
    [4, 5],
    [5, 6],
    [5, 7],
    [6, 8],
    [7, 8],
    [8, 9]
]

var friendships = {}
each(users, fn(e, i) {
    set(friendships, e["id"], [])
})
each(friendship_pairs, fn(e, i) {
    set(friendships, e[0], friendships[e[0]] + e[1])
    set(friendships, e[1], friendships[e[1]] + e[0])
})
print("Friendships: ", friendships, nl)

var number_of_friends = fn(u) {
    var user_id = u["id"]
    var friend_ids = friendships[user_id]
    return len(friend_ids)
}
var temp = []
each(users, fn(e, i) {
    var temp = temp + number_of_friends(e)
})
var total_connections = sum(temp)
print("Total connections: ", total_connections, nl)

var num_users = len(users)
var avg_connections = total_connections / num_users
print("Average connections: ", avg_connections, nl)

var num_friends_by_id = []
each(users, fn(e, i) {
    var num_friends_by_id = num_friends_by_id + [e["id"], number_of_friends(e)]
})
print("Number of friends by id (not sorted): ", num_friends_by_id, nl)

sort_rect_array_of_number_by_index(num_friends_by_id, 1)
print("Number of friends by id (sorted asc): ", num_friends_by_id, nl)
reverse(num_friends_by_id)
print("Number of friends by id (sorted desc): ", num_friends_by_id, nl)
println("Note: [user_id, num_friends] order differs from the illustrated output 
  in the book, but the array is still sorted, based on num_friends")