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Standard Deviation in Swift
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func standardDeviation(arr : [Double]) -> Double | |
{ | |
let length = Double(arr.count) | |
let avg = arr.reduce(0, {$0 + $1}) / length | |
let sumOfSquaredAvgDiff = arr.map { pow($0 - avg, 2.0)}.reduce(0, {$0 + $1}) | |
return sqrt(sumOfSquaredAvgDiff / length) | |
} | |
let responseTimes = [ 18.0, 21.0, 41.0, 42.0, 48.0, 50.0, 55.0, 90.0 ] | |
standardDeviation(responseTimes) // 20.8742514835862 | |
standardDeviation([2,4,4,4,5,5,7,9]) // 2.0 |
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also, I think
.reduce(0, {$0 + $1})
can be simplified to.reduce(0, +)
.