association.py 文件源码

def fisher(cls, *marginals):
        """Scores bigrams using Fisher's Exact Test (Pedersen 1996).  Less
        sensitive to small counts than PMI or Chi Sq, but also more expensive
        to compute. Requires scipy.
        """

        n_ii, n_io, n_oi, n_oo = cls._contingency(*marginals)

        (odds, pvalue) = fisher_exact([[n_ii, n_io], [n_oi, n_oo]], alternative='less')
        return pvalue