get the half normal matrix attribute.  Create the attribute if
        it has not yet been created

        Returns
        -------
        qhalfx : pyemu.Matrix

def qhalfx(self):
        """get the half normal matrix attribute.  Create the attribute if
        it has not yet been created

        Returns
        -------
        qhalfx : pyemu.Matrix

        """
        if self.__qhalfx is None:
            self.log("qhalfx")
            self.__qhalfx = self.qhalf * self.jco
            self.log("qhalfx")
        return self.__qhalfx