Friends
I'm trying fit a survival model by maximum likelihood estimation using this
function:
flver=function(a1,a2,b1,b2)
{
lver=-(sum(st*log(exp(a1*x1+a2*x2)))+sum(st*log(hheft(exp(b1*x1+b2*x2)*t,f.heft)))
-(exp(a1*x1+a2*x2)/exp(b1*x1-b2*x2))*sum(-log(1-pheft(exp(b1*x1+b2*x2)*t,f.heft))))
}
emv=mle(flver,start=list(a1=0,a2=0,b1=0,b2=0))
where hheft and pheft are functions defined in polspline package.
My variables are:
t: time
st: censor
x1 and x2: Covariates
I don't find any estimation because an error occurs:
Non finite/finite difference value [0].
Can I treat this error? I try using "SANN" method and this error occurs too. There is
another alternative?
Thanks
Olympio Neto
[[alternative HTML version deleted]]
______________________________________________
[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
