simpleMovingAverage

extension Array where Element: FloatingPoint {
    func simpleMovingAverage(scope:Int) -> [Element]? {
        guard self.count >= scope else { return nil }
        var result = [Element]()
        for endIndex in scope...self.count {
            let lower = endIndex-scope
            let upper = endIndex
            let range = Range(uncheckedBounds: (lower: lower, upper: upper))
            let sum = self[range].reduce(0) { (v1, v2) -> Element in return v1+v2 }
            let avg = sum/Element(scope)
            result.append(avg)
        }
        return result
    }
}

/// try this with swift playground
//let case1 = ((Array<Int>)(0...180)).map{Double($0) + Double(arc4random_uniform(300))/10}.simpleMovingAverage(scope: 10)
//let case2 = ((Array<Int>)(0...9)).map{Double($0) + Double(arc4random_uniform(300))/10}.simpleMovingAverage(scope: 10)
//let case3 = ((Array<Int>)(0...8)).map{Double($0) + Double(arc4random_uniform(300))/10}.simpleMovingAverage(scope: 10)
//case1
//case2
//case3