Fit coords (x,y,[z]) so that distances from reference coordinates
        match closest to reference distances

def _analytical_fit_adjacent(self, ref_dists):
        """
        Fit coords (x,y,[z]) so that distances from reference coordinates
        match closest to reference distances
        """
        dists = ref_dists**2
        rot_dists = self._rotate_rows(dists)
        b = dists - rot_dists + self._partial_b
        self._b = b
        return self._pinvA.dot(b)