[R] over/under flow

William H. Asquith wasquith at austin.rr.com
Sun Jul 3 22:02:25 CEST 2005

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),

but I am not sure how to invert or solve for OVER


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