Hello,
If i write a function as below using log of weibull distribution i do not get the required 

results in estimating the parameters what do i do, please

a/b * (t/b)^a-1 * exp(-t/b)^a


n=500
x<-rweibull(n,2,2)
z<-function(p) {(-n*log(p[1])+n*log(p[2])-
(p[1]-1)*sum(log(x))+(p[1]-1)*log(p[2])+(sum(x/p[2])^(p[1]))  )}
zz<-optim(c(0.5,0.5),z)
zz
	[[alternative HTML version deleted]]

