Swift playgrounds code to filter Wikimedia browser stats

Wikimedia.swift

import Foundation

let tab = CharacterSet(charactersIn: "\t")
let newline = CharacterSet(charactersIn: "\n")
let fmt = DateFormatter() ; fmt.dateFormat = "YYYY-mm-DD"

let dateRanges = [
    (fmt.date(from: "2015-01-01"), fmt.date(from: "2016-01-01")),
    (fmt.date(from: "2016-01-01"), fmt.date(from: "2017-01-01")),
    (fmt.date(from: "2017-01-01"), fmt.date(from: "2018-01-01")),
]

struct DataPoint {
    let os, osVersion, browser, browserVersion: String
    let value: Double
    let date: Date

    init(os: String, osVersion: String, browser: String, browserVersion: String, value: Double, date: Date)
    {
        self.os = os
        self.osVersion = osVersion
        self.browser = browser
        self.browserVersion = browserVersion
        self.value = value
        self.date = date
    }

    init?(string s: String) {
        let comps = s.components(separatedBy: tab)
        guard comps.count == 6,
            let v = comps.last as NSString?,
            let d = fmt.date(from: comps[0])
          else { return nil }

        self.init(os: comps[1], osVersion: comps[2],
                  browser: comps[3], browserVersion: comps[4],
                  value: v.doubleValue, date: d)
    }
}

func readStats() -> String {
    let url = URL(string: "https://analytics.wikimedia.org/datasets/periodic/reports/metrics/browser/all_sites_by_os_and_browser_percent.tsv")
    return try! String(contentsOf: url!)
}

func ratio(browser: String, data: [DataPoint]) -> Double {
    let browserSum = data.filter    { $0.browser == browser }
                         .reduce(0) { $0 + $1.value }
    let allSum = data.reduce(0) { $0 + $1.value }

    return browserSum / allSum
}

let osxData = readStats()
    .components(separatedBy: newline)
    .flatMap { DataPoint.init(string: $0) }
    .filter { $0.os == "Mac OS X" }

for (start, end) in dateRanges {
    guard let start = start, let end = end else { continue }

    let rangedData = osxData.filter { start <= $0.date && $0.date < end }

    let safariPercentage = ratio(browser: "Safari", data: rangedData) * 100.0
    let chromePercentage = ratio(browser: "Chrome", data: rangedData) * 100.0

    let dateRange = "\(fmt.string(from: start)) - \(fmt.string(from: end))"
    let output = String(format: "%@ Safari: %2.1f%% Chrome: %2.1f%%", dateRange, safariPercentage, chromePercentage)
    print(output)
}

Refactored this to have a bit nicer structure and it now reports the Safari and Chrome results by time ranges.

Running this on Swift Playground or Xcode Playground results in

2015-01-01 - 2016-01-01 Safari: 51.4% Chrome: 36.7%
2016-01-01 - 2017-01-01 Safari: 49.2% Chrome: 39.7%
2017-01-01 - 2018-01-01 Safari: 46.4% Chrome: 41.4%