Average cationic radius for element (with units). The average is
        taken over all positive oxidation states of the element for which
        data is present.

def average_cationic_radius(self):
        """
        Average cationic radius for element (with units). The average is
        taken over all positive oxidation states of the element for which
        data is present.
        """
        if "Ionic radii" in self._data:
            radii = [v for k, v in self._data["Ionic radii"].items()
                     if int(k) > 0]
            if radii:
                return sum(radii) / len(radii)
        return 0