def setcoef(self, Z):
        """Set coefficient array."""

        self.Z = np.asarray(Z, dtype=self.dtype)
        self.SZT = self.S.dot(Z.T)
        # Factorise dictionary for efficient solves
        self.lu, self.piv = sl.lu_factor(Z, self.rho)
        self.lu = np.asarray(self.lu, dtype=self.dtype)