trigamma                package:MASS                R Documentation

_T_r_i_g_a_m_m_a _F_u_n_c_t_i_o_n

_D_e_s_c_r_i_p_t_i_o_n:

     Calculates the trigamma function, which is the second derivative
     of the logarithm of the gamma function, for complex vector
     arguments.

_U_s_a_g_e:

     trigamma(z)

_A_r_g_u_m_e_n_t_s:

       z: Vector argument.  May be real or complex but must have
          positive real part. 

_D_e_t_a_i_l_s:

     Uses an asymptotic expansion where Re(z) > 5 and a recurrence
     formula to such a case where Re(z) <= 5.  Accuracy is good.

_V_a_l_u_e:

     Vector of trigamma(z) values.

_R_e_f_e_r_e_n_c_e_s:

     M. Abramowitz and I. A. Stegun (1965) Handbook of Mathematical
     Functions. Dover.

_S_e_e _A_l_s_o:

     `digamma'

