Must be greater than b if |z| < 1, and c > b + a if z = 1
z
|z|
method
The default is to use the Cephes library
routine. This sometimes is unstable for large a or z near one
returning Inf or negative values. In this case, try
method="Laplace", which use a Laplace approximation for tau = exp(t/(1-t)).
log
if TRUE, return log(2F1)
Value
if log=T returns the log of the 2F1 function; otherwise the 2F1 function.
Details
The
default is to use the routine hyp2f1.c from the Cephes library. If that
return a negative value or Inf, one should try method="Laplace" which
is based on the Laplace approximation as
described in Liang et al JASA 2008. This is used in the hyper-g prior
to calculate marginal likelihoods.
References
Cephes library hyp2f1.c
Liang, F., Paulo, R., Molina, G., Clyde, M. and Berger,
J.O. (2005) Mixtures of g-priors for Bayesian Variable
Selection. Journal of the American Statistical Association
http://www.stat.duke.edu/05-12.pdf