On Thu, 30 Aug 2007, willem vervoort wrote: > Dear all, > I am struggling to understand this. > > What happens when you raise a negative value to a power and the result > is a very large number?
Where are the 'very large numbers' here? R can cope with much larger numbers (over 10^300). > B > [1] 47.73092 > >> -51^B > [1] -3.190824e+81 Yes, that is -(51^B). > # seems fine > # now this: >> x <- seq(-51,-49,length=100) > >> x^B > [1] NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN NaN > <snip> >> is.numeric(x^B) > [1] TRUE >> is.real(x^B) > [1] TRUE >> is.infinite(x^B) > [1] FALSE FALSE FALSE FALSE FALSE > > I am lost, I checked the R mailing help, but could not find anything > directly. I loaded package Brobdingnag and tried: > as.brob(x^B) > [1] NAexp(NaN) NAexp(NaN) NAexp(NaN) NAexp(NaN) NAexp(NaN) >> as.brob(x)^B > > I guess I must be misunderstanding something fundamental. You are. A negative number to a non-integer power is undefined in the real number system. Look at (x+0i)^B. -- 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-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 and provide commented, minimal, self-contained, reproducible code.