def vspec(data):
    """
    Takes the vector mean of replicate measurements at a given step
    """
    vdata, Dirdata, step_meth = [], [], []
    tr0 = data[0][0]  # set beginning treatment
    data.append("Stop")
    k, R = 1, 0
    for i in range(k, len(data)):
        Dirdata = []
        if data[i][0] != tr0:
            if i == k:  # sample is unique
                vdata.append(data[i - 1])
                step_meth.append(" ")
            else:  # sample is not unique
                for l in range(k - 1, i):
                    Dirdata.append([data[l][1], data[l][2], data[l][3]])
                dir, R = vector_mean(Dirdata)
                vdata.append([data[i - 1][0], dir[0], dir[1],
                              old_div(R, (i - k + 1)), '1', 'g'])
                step_meth.append("DE-VM")
            tr0 = data[i][0]
            k = i + 1
            if tr0 == "stop":
                break
    del data[-1]
    return step_meth, vdata
Takes the vector mean of replicate measurements at a given step