On Wed, 10 Oct 2007, Duncan Murdoch wrote:> > As Charles Berry told you when this was posted to R-help, it looks as > though it is Mathematica that is inaccurate. For example, I would > expect this plot to be smooth, and it is not in either R or Mathematica, > but R is at least monotone:
I did check this on Maple by integrating the density function and got about 11-12 digits accuracy at df=88. I also tried replacing 1e-4 with an exactly-representable number (3/32768), with a similar accuracy level. pbeta() claims 14-digit accuracy and is called by pt() with 1/(1+x^2/n) as its argument. I would have thought that the 1/(1+x^2/n) could easily be responsible for this sort of accuracy loss when x=1e-4. If so, it may not be easy to improve. -thomas ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel