Created
January 7, 2013 16:21
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| # http://bateru.com/news/2011/03/javascript-standard-deviation-variance-average-functions/ | |
| getNumWithSetDec = (num, numOfDec = 3) -> | |
| pow10s = Math.pow(10, numOfDec) | |
| (if (numOfDec) then Math.round(pow10s * num) / pow10s else num) | |
| getAverageFromNumArr = (numArr, numOfDec) -> | |
| return false unless _.isArray(numArr) | |
| i = numArr.length | |
| sum = 0 | |
| sum += numArr[i] while i-- | |
| getNumWithSetDec (sum / numArr.length), numOfDec | |
| getVariance = (numArr, numOfDec) -> | |
| return false unless _.isArray(numArr) | |
| avg = getAverageFromNumArr(numArr, numOfDec) | |
| i = numArr.length | |
| v = 0 | |
| v += Math.pow((numArr[i] - avg), 2) while i-- | |
| v /= numArr.length | |
| getNumWithSetDec v, numOfDec | |
| getStandardDeviation = (numArr, numOfDec) -> | |
| return false unless _.isArray(numArr) | |
| stdDev = Math.sqrt(getVariance(numArr, numOfDec)) | |
| getNumWithSetDec stdDev, numOfDec |
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