def pr_hoelder_mean(self, exp=<NUM_LIT:2>):
return hoelder_mean((self.precision(), self.recall()), exp)<EOL>
r"""Return Hölder (power/generalized) mean of precision & recall.

        The power mean of precision and recall is defined as:
        :math:`\frac{1}{2} \cdot
        \sqrt[exp]{precision^{exp} + recall^{exp}}`
        for :math:`exp \ne 0`, and the geometric mean for :math:`exp = 0`

        Cf. https://en.wikipedia.org/wiki/Generalized_mean

        Parameters
        ----------
        exp : float
            The exponent of the Hölder mean

        Returns
        -------
        float
            The Hölder mean for the given exponent of the confusion table's
            precision & recall

        Example
        -------
        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.pr_hoelder_mean()
        0.8290638930598233