

   TThhee DDiiggaammmmaa FFuunnccttiioonn

        digamma(z)

   AArrgguummeennttss::

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

   DDeessccrriippttiioonn::

        Calculates the digamma function, which is the first
        derivative of the logarithm of the gamma function, for
        complex vector arguments.

   DDeettaaiills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Vaalluuee::

        Vector of digamma(z) values.

   RReeffeerreenncceess::

        M. Abramowitz and I. A. Stegun (1965) Handbook of Math-
        ematical Functions.  Dover.

   SSeeee AAllssoo::

        `trigamma'

