Question

How to calculate the mean and the standard deviation of a sequence of floating-point values in Swift

Answer 1

import Foundation

func calculateMean(_ data: [Double]) -> Double {
    guard !data.isEmpty else { return 0.0 }
    
    let sum = data.reduce(0, +)
    
    return sum / Double(data.count)
}

func calculateStandardDeviation(_ data: [Double], mean: Double) -> Double {
    guard data.count > 1 else { return 0.0 }
    
    let sumOfSquaredDiffs = data.map { pow($0 - mean, 2) }.reduce(0, +)
    let variance = sumOfSquaredDiffs / Double(data.count - 1)
    
    return sqrt(variance)
}

let numbers: [Double] = [3.4, 1.8, 4.3, 5.0, 6.2]

let mean = calculateMean(numbers)
let stddev = calculateStandardDeviation(numbers, mean: mean)

print(String(format: "Mean: %.2f", mean))
print(String(format: "Standard Deviation: %.2f", stddev))



/*
run:

Mean: 4.14
Standard Deviation: 1.66

*/

 

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