_V_e_r_i_f_y _t_h_a_t _a_n _o_b_j_e_c_t _i_s _o_f _c_l_a_s_s _r_a_t_e_t_a_b_l_e. _T_h_e _f_u_n_c_t_i_o_n
	_v_e_r_i_f_i_e_s _n_o_t _o_n_l_y _t_h_e _c_l_a_s_s _a_t_t_r_i_b_u_t_e, _b_u_t _t_h_e _s_t_r_u_c_t_u_r_e _o_f
	_t_h_e _o_b_j_e_c_t.
	
	     is.ratetable(x, verbose=F)
	
	_A_r_g_u_m_e_n_t_s:
	
	            x:
	     the object to be verified.
	
	      verbose:
	     if TRUE and the object is not a ratetable, then return
	     a character string describing the way(s) in which x
	     fails to be a proper ratetable object.
	
	     Value:
	
	     returns TRUE if x is a ratetable, and FALSE or a
	     description if it is not.  Rate tables are used by the
	     pyears and survexp functions, and normally contain
	     death rates for some population, categorized by age,
	     sex, or other variables.  They have a fairly rigid
	     structure, and the verbose option can help in creating
	     a new rate table.
	
	     pyears, survexp