_O_r_d_e_r_i_n_g _P_e_r_m_u_t_a_t_i_o_n
	
	     order(...)
	
	_A_r_g_u_m_e_n_t_s:
	
	         ... : a sequence of vectors.
	
	_D_e_s_c_r_i_p_t_i_o_n:
	
	     order returns a permutation which will rearrange its
	     first argument into ascending order.  In the case of
	     ties in the first vector, values in the second are used
	     to break the ties.  If the values are still tied,
	     values in the later arguments are used to break the
	     tie.
	
	     NA values are treated as greater than any other values
	     so that permutations returned by order move NA values
	     to the top end of the array.
	
	_E_x_a_m_p_l_e_s:
	
	     # rearrange matched vectors so that
	     # the first is in ascending order
	     o <- order(x)
	     x <- x[o]
	     y <- y[o]