Great, but to followup, how do I select the bounds (B,E) on the root for an arbitrary machine?
OVER = uniroot(function(x) lgamma(x)-log(.Machine$double.xmax), c(B,E))$root If uniroot() is fast enough, is it appropriate for me to set B at say 1 and E at log(.Machine$double.max)? Suggestions on do this the proper "R way"? Perhaps this . . . OVER = uniroot(function(x) lgamma(x)-log(.Machine$double.xmax), c(1,log(.Machine$double.xmax)))$root I am working on a package so different machines will be involved thus simple 171,172 might not be the best idea for the root? THANKS! -wha On Jul 3, 2005, at 3:43 PM, Peter Dalgaard wrote: > "William H. Asquith" <[EMAIL PROTECTED]> writes: > >> I am porting some FORTRAN to R in which an Inf triggers an if(). The >> trigger is infinite on exp(lgamma(OVER)). What is the canonical R >> style of determining OVER when exp(OVER)== Inf? The code structure >> that I am >> porting is best left intact--so I need to query R somehow to the value >> of OVER that causes exp(lgamma(OVER)) to equal Inf. >> >> On my system, >> exp(lgamma(171)) is about first to equal Inf. >> >> I asked similar question a few weeks ago on exp(OVER) and got the >> answer back as log(.Machine$double.xmax). I now have the lgamma >> involved. I think that answer is what is OVER such the >> >> .Machine$double.xmax = lgamma(OVER), > > Not quite... (see below) > >> but I am not sure how to invert or solve for OVER > > >> uniroot(function(x) lgamma(x)-log(.Machine$double.xmax), c(171,172)) > $root > [1] 171.6244 > > $f.root > [1] -1.462051e-07 > > $iter > [1] 3 > > $estim.prec > [1] 6.103516e-05 > > > -- > O__ ---- Peter Dalgaard Øster Farimagsgade 5, Entr.B > c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K > (*) \(*) -- University of Copenhagen Denmark Ph: (+45) > 35327918 > ~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: (+45) > 35327907 > ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
