def centralize(self):
        # Centralize the data
        # use mean or median
        centerX = np.mean(self._points[:,0])
        centerY = np.mean(self._points[:,1])
        centerZ = np.mean(self._points[:,2])
        self._points[:,0] -= np.int16(centerX)
        self._points[:,1] -= np.int16(centerY)
        self._points[:,2] -= np.int16(centerZ)
        return self