rbeta(100,0.1,0.1) is generating samples which contain 1, an impossible value for a beta and hence the sample has an infinite log-likelihood. It is clearly documented on the help page that the range is 0 < x < 1. However, that is not so surprising as P(X > 1-1e-16) is about 1% and hence values will get rounded to one.
The same would happen for a value of 0. Your code is syntactically incorrect, at least as received here. On Fri, 4 Jul 2003, Agustin Lobo wrote: > > I have the following problem: > > I have a vector x of data (0<x<=1 ) with > a U-shaped histogram and try to fit a beta > distribution using fitdistr. In fact, > hist(rbeta(100,0.1,0.1)) looks a lot like > my data. > > The equivalent to > the example in the manual > sometimes work: > > > a <- rbeta(100,0.1,0.1) > > fitdistr(x=a, "beta", start=list(shape1=0.1,shape2=0.1))1) > > shape1 shape2 > 0.09444627 0.12048753 > (0.01120670) (0.01550129) > > but sometimes does not: > > a <- rbeta(100,0.1,0.1) > > fitdistr(x=a, "beta", start=list(shape1=0.1,shape2=0.1))1) > > Error in optim(start, mylogfn, x = x, hessian = TRUE, ...) : > Function cannot be evaluated at initial parameters > > Unfortunately, my data fall in the second case > > I've searched for any weird value that be present in the > cases in which fitdistr exits with the error message, but > could not find any. > > Any help? > (please if anyone answers be sure to answer to my address as well, > I cannot subscribe to the list) > > Thanks > > Agus > > Dr. Agustin Lobo > Instituto de Ciencias de la Tierra (CSIC) > Lluis Sole Sabaris s/n > 08028 Barcelona SPAIN > tel 34 93409 5410 > fax 34 93411 0012 > [EMAIL PROTECTED] > > ______________________________________________ > [EMAIL PROTECTED] mailing list > https://www.stat.math.ethz.ch/mailman/listinfo/r-help > -- 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 ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
