My script for calculating the statistical moments of an array in coffeescript

moments.coffee

moments = (arr, doMedian=false) ->

    length = arr.length
    sum = arr.reduce (t, s) -> t + s
    mean = sum / length

    averageDeviation = 0.0
    averageDeviation = 0.0
    standardDeviation = 0.0
    variance = 0.0
    skew = 0.0
    kurtosis = 0.0

    minimum = null
    maximum = null

    for val in arr
        d = val - mean
        averageDeviation += Math.abs(d)

        d *= d
        variance += d
        d *= d
        skew += d
        d *= d
        kurtosis += d

        if minimum is null or val < minimum
            minimum = val
        if maximum is null or val > maximum
            maximum = val

    averageDeviation /= length
    variance /= (length - 1)
    standardDeviation = Math.sqrt(variance)

    if variance > 0.0
        skew /= (length * variance * standardDeviation)
        kurtosis = kurtosis/(length * Math.pow(variance, 2)) - 3.0

    retval = {
        "sum": sum,
        "mean": mean,
        "minimum": minimum,
        "maximum": maximum,
        "averageDeviation": averageDeviation,
        "standardDeviation": standardDeviation,
        "variance": variance,
        "skew": skew,
        "kurtosis": kurtosis,
    }

    # Finding the median requires copying & sorting the array, so we don't
    # return it by default.
    if doMedian

        sortedArr = arr.slice()
        sortedArr.sort()
        midPoint = Math.floor(length / 2)

        # When there is no unique median, take the mean
        # of the two closest
        if length % 2 == 0
            median = (sortedArr[midPoint] + sortedArr[midPoint-1]) / 2
        else
            median = sortedArr[midPoint]

        retval.median = median

    return retval