On Mon, 15 Oct 2007, Thomas Yee wrote: > Hello, > > I was wondering if the functions deriv3(), deriv() etc. could be extended > to handle psigamma() and its special cases (digamma(), trigamma() > etc.). From the error message it seems that 'psigamma' needs to be > added to the derivatives table. > This might be easy since psigamma() has a deriv argument.
If you look at ?deriv you will see that it only knows about functions *of one argument* and operators. So it would be easy to add digamma(x) and psigamma(x) (and I will do so shortly), it would not be so easy to add psigamma(x, deriv). > Additionally, this error message is also obtained when requesting for > the Hessian of the gamma and lgamma functions: > > d3 = deriv(~ gamma(y), namev="y", hessian= TRUE) > d3 = deriv(~ lgamma(y), namev="y", hessian= TRUE) > > Another class of special functions worth adding are the Bessel functions. Well, you can always submit a patch .... Note that deriv() in R differs from that in S in being done in C and hence not being user-extensible. A long time ago that had an advantage: S's deriv could be very slow and take a lot of memory by the standards of the early 1990's. Rather than work on adding yet more special cases it would seem better to work on making it user-extensible. -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel