def vc(self):
        """
        Direct quote from Gries (2019)
        A maybe more useful variant of this measure is its normalized version, the variation
        coefficient (vc, see (9)); the normalization consists of dividing sdpopulation by the mean frequency
        of the element in the corpus parts f/n:
        """
        ss = StandardScaler(with_mean=False).fit(self.term_part_counts)
        return np.sqrt(ss.var_) / ss.mean_

        Direct quote from Gries (2019)
        A maybe more useful variant of this measure is its normalized version, the variation
        coefficient (vc, see (9)); the normalization consists of dividing sdpopulation by the mean frequency
        of the element in the corpus parts f/n:
        
scattertext/dispersion/dispersion.py