[R] R: Help; error in optim

[Christopher Kelvin]

Hello,
When i run the code below from Weibull distribution with 30% censoring by using optim i get an error form R, which states that


Error in optim(start, fn = z, data = q, hessian = T) : 
  objective function in optim evaluates to length 25 not 1

can somebody help me remove this error. Is my censoring approach correct.

n=25;rr=1000
p=1.5;b=1.2
for (i in 1:rr){
q<-c(t,cen)
t<-rweibull(25,shape=p,scale=b)
meantrue<-gamma(1+(1/p))*b
meantrue
d<-meantrue/0.30
cen<- runif(25,min=0,max=d)
cen
s<-ifelse(t<=cen,1,0)

z<-function(data,p){ 
beta<-p[1]
eta<-p[2]
log1<-(n*cen*log(p[1])-n*cen*(p[1])*log(p[2])+cen*(p[1]-1)*sum(log(t))-n*sum((t/(p[2]))^(p[1])))
return(-log1)
}
start <-c(0.5,0.5)
zz<-optim(start,fn=z,data=q,hessian=T)

m1<-zz$par[2]
p<-zz$par[1]

}
m1
p

Thank you

Chris Guure
Researcher
Institute for Mathematical Research
UPM