_L_a_g_g_e_d _D_i_f_f_e_r_e_n_c_e_s
	
	     diff(x, lag=1, differences=1)
	
	_A_r_g_u_m_e_n_t_s:
	
	           x : a numeric vector or matrix containing the
	               values to be differenced.
	
	         lag : an integer indicating which lag to use.
	
	 differences : an integer indicating the order of the
	               difference.
	
	_V_a_l_u_e:
	
	     If x is a vector of length n and differences=1, then
	     the computed result is equal to the successive differ-
	     ences x[(1:n-lag)]-x[(lag:n)].  If difference is larger
	     than one this algorithm is applied recursively to x.
	     Note that the returned value is a vector which is
	     shorter than x.
	
	     If x is a matrix then the difference operations are
	     carried out on each column separately.
	
	     NA's propagate.
	
	_E_x_a_m_p_l_e_s:
	
	     diff(1:10, 2)
	     diff(1:10, 2, 2)