so my chi-square approximation was not very good: > pchisq(39540, 1, lower.tail=FALSE, log.p=TRUE) [1] -19775.52 > (pchisq(39540, 1, lower.tail=FALSE, log.p=TRUE) + /log(10)) [1] -8588.398
... roughly 1e-8588. With a few hours with Abramowitz and Stegun, I suspect I could do better. spencer graves David Duffy wrote: >>This is obtained from F =39540 with df1 = 1, df2 = 7025. >>Suppose am interested in exact value such as >> > > > If it were really necessary, you would have to move to multiple > precision. The gmp R package doesn't seem to yet cover this, but FMLIB > (TOMS814, DM Smith) is a multiple precision f90 library that does > include the incomplete beta -- it allows one to say for F(1,7025)=39540, > P=6.31E-2886 (evaluated using 200 sign. digit arithmetic). Results from > R's pf() agree quite closely with the FMLIB results for less extreme values > eg > >>print(pf(1500,1,7025,lower=FALSE), digits=20) > > [1] 1.3702710894887480597e-297 > > cf 1.37027108948832580215549799419452388134616261215463681945E-297 > > > | David Duffy (MBBS PhD) ,-_|\ > | email: [EMAIL PROTECTED] ph: INT+61+7+3362-0217 fax: -0101 / * > | Epidemiology Unit, Queensland Institute of Medical Research \_,-._/ > | 300 Herston Rd, Brisbane, Queensland 4029, Australia GPG 4D0B994A v > > ______________________________________________ > R-help@stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html -- Spencer Graves, PhD Senior Development Engineer PDF Solutions, Inc. 333 West San Carlos Street Suite 700 San Jose, CA 95110, USA [EMAIL PROTECTED] www.pdf.com <http://www.pdf.com> Tel: 408-938-4420 Fax: 408-280-7915 ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html