Please do as the FAQ asked you to, and check the NEWS file at https://svn.R-project.org/R/trunk/NEWS
R 2.6.2 is not the '_next_ release of R', and that pre-release behaves differently as documented in the NEWS file. On Fri, 15 Feb 2008, [EMAIL PROTECTED] wrote: > While I agree that the reported results from Mathematica have only 10-13 > correct digits, that does not mean that pt() in R is any better for these > calculations. For instance the following three calculations are > mathematically equivalent, but pt() disagrees at the 13th figure in R > v2.6.2 > pt(1e-4,13) > pf(1e-8,1,13)/2+0.5 > pbeta(1/(1+13/1e-8),.5,6.5)/2+0.5 > Using 1/(1+n/x^2) and reversing the shape parameters avoids the accuracy > loss that Thomas Lumley was concerned about. > > The following reference values for pt(1e-4,1:100) were computed in Maple > to 400 figures and then rounded to 17. To 17 figures, there was no > difference in the results whether I used the exact value of 10^(-4) or the > exact binary double precision approximation of 7378697629483821*2^(-66). > Compared to these reference values, log relative errors (LRE, essentially > the number of correct figures) for pt ranged from 10.7 to 13.4, while > pf(1e-8,1,df)/2+0.5 > and > pbeta(1/(1+df/1e-8),.5,df/2)/2+0.5 > agreed exactly with Maple, except for 21 and 90 df, where the LRE was > 15.65. Clearly it would be quite easy to improve pt() for small values of > x. > > > Jerry W. Lewis > Lead Statistician > Biogen Idec > Cambridge, MA USA > > > z<-c(0.50003183098851228, 0.50003535533897094, 0.50003675525961311, > 0.50003749999992188, 0.50003796066890633, 0.50003827327715657, > 0.50003849914500990, 0.50003866990202363, 0.50003880349081531, > 0.50003891083832527, 0.50003899897563476, 0.50003907263045176, > 0.50003913509812855, 0.50003918874550927, 0.50003923531621426, > 0.50003927612297732, 0.50003931217293135, 0.50003934425160310, > 0.50003937298066018, 0.50003939885850220, 0.50003942228935944, > 0.50003944360452316, 0.50003946307808180, 0.50003948093875281, > 0.50003949737889518, 0.50003951256145633, 0.50003952662538506, > 0.50003953968989187, 0.50003955185783298, 0.50003956321842127, > 0.50003957384941549, 0.50003958381890103, 0.50003959318674852, > 0.50003960200581637, 0.50003961032294799, 0.50003961817980360, > 0.50003962561355779, 0.50003963265748728, 0.50003963934146876, > 0.50003964569240221, 0.50003965173457262, 0.50003965748996017, > 0.50003966297850729, 0.50003966821834945, 0.50003967322601522, > 0.50003967801660046, 0.50003968260392016, 0.50003968700064152, > 0.50003969121840071, 0.50003969526790563, 0.50003969915902671, > 0.50003970290087718, 0.50003970650188431, 0.50003970996985278, > 0.50003971331202108, 0.50003971653511200, 0.50003971964537768, > 0.50003972264864014, 0.50003972555032763, 0.50003972835550734, > 0.50003973106891495, 0.50003973369498129, 0.50003973623785651, > 0.50003973870143192, 0.50003974108935987, 0.50003974340507184, > 0.50003974565179484, 0.50003974783256646, 0.50003974995024854, > 0.50003975200753972, 0.50003975400698688, 0.50003975595099569, > 0.50003975784184024, 0.50003975968167193, 0.50003976147252762, > 0.50003976321633717, 0.50003976491493036, 0.50003976657004330, > 0.50003976818332434, 0.50003976975633955, 0.50003977129057782, > 0.50003977278745549, 0.50003977424832079, 0.50003977567445783, > 0.50003977706709040, 0.50003977842738546, 0.50003977975645637, > 0.50003978105536601, 0.50003978232512953, 0.50003978356671702, > 0.50003978478105603, 0.50003978596903380, 0.50003978713149950, > 0.50003978826926618, 0.50003978938311274, 0.50003979047378564, > 0.50003979154200064, 0.50003979258844427, 0.50003979361377541, > 0.50003979461862660) > [[alternative HTML version deleted]] > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > -- 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