def pr_cmean(self):
return cmean((self.precision(), self.recall()))<EOL>
r"""Return contraharmonic mean of precision & recall.

        The contraharmonic mean is:
        :math:`\frac{precision^{2} + recall^{2}}{precision + recall}`

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

        Returns
        -------
        float
            The contraharmonic mean of the confusion table's precision & recall

        Example
        -------
        >>> ct = ConfusionTable(120, 60, 20, 30)
        >>> ct.pr_cmean()
        0.8295566502463055