sequence function: apply-normed-frequency-class

    description:
        apply-normed-frequency-class(e, X)
        finds the normed frequency class of e in X,
        then returns ket(e.label, nfc(e, X))

    the algorithm:
        drop all elements <= 0 from X
        smallest = the min coeff in X
        largest = the max coeff in X
        f = the value of e.label in X

        if largest <= 0 or f <= 0:
            return 0
        fc_max = math.floor(0.5 - math.log(smallest / largest, 2)) + 1
        return 1 - math.floor(0.5 - math.log(f / largest, 2)) / fc_max

    examples:

    see also:
        normed-frequency-class