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 0.12048753fitdistr(x=a, "beta", start=list(shape1=0.1,shape2=0.1))1)

shape1 shape2

(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 parametersfitdistr(x=a, "beta", start=list(shape1=0.1,shape2=0.1))1)

Error in optim(start, mylogfn, x = x, hessian = TRUE, ...) :

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

alobo at ija.csic.es