Question

让我们说我正在计算1到100的随机数。我希望数字随机选择，但是我可以设置偏差，更可能选择中心。因此，如果我做随机样本可以说一千次，那么将会更频繁地选择中心数字。它选择中心的数量应该基于我在didHitChanceOf函数中设置的数字。这样做的最佳方式是什么？

我目前的代码没有做到这一点，甚至是随机性的

当前非偏向随机数代码（Swift 3）

extension Int
{
    static func random(range: ClosedRange<Int> ) -> Int
    {
        var offset = 0

        if range.lowerBound < 0   // allow negative ranges
        {
            offset = abs(range.lowerBound)
        }

        let mini = UInt32(range.lowerBound + offset)
        let maxi = UInt32(range.upperBound   + offset)

        return Int(mini + arc4random_uniform(maxi - mini)) - offset
    }
}

func didHitChanceOf(chance: Double) -> Bool{
        let random = Int.random(range: 0...100)
        if(Double(random) < chance){ //If the conversion rate is 20%, then only 20% of the time will the random number be less than the conversion rate.
            return true
        }else{
            return false
        }
    }
var adwordsClicks = 500
let adwordsConversionRate = 20
var adwordsConversions = 0
for _ in 0...adwordsClicks {
            if(didHitChanceOf(chance: adwordsConversionRate) == true){
                adwordsConversions = adwordsConversions + 1
            }
        }

Answer 1

您可以使用GameKit中的GKGaussianDistribution（也称为正态分布）来执行此操作。您需要2个参数：mean（＆＃34;中心＆＃34;您想要的）和deviation（它应该从中心传播多远）：

import GameKit

func random(count: Int, in range: ClosedRange<Int>, mean: Int, deviation: Int) -> [Int] {
    guard count > 0 else { return [] }

    let randomSource = GKARC4RandomSource()
    let randomDistribution = GKGaussianDistribution(randomSource: randomSource, mean: Float(mean), deviation: Float(deviation))

    // Clamp the result to within the specified range
    return (0..<count).map { _ in
        let rnd = randomDistribution.nextInt()

        if rnd < range.lowerBound {
            return range.lowerBound
        } else if rnd > range.upperBound {
            return range.upperBound
        } else {
            return rnd
        }
    }
}

用法和测试：

let arr = random(count: 1_000_000, in: 0...100, mean: 70, deviation: 10)

let summary = NSCountedSet(array: arr)
for i in 0...100 {
    print("\(i): \(summary.count(for: i))")
}

您可以看到70左右的值具有最高计数

Swift 3：如何计算偏向偏向的随机数

1 个答案: