[R] survreg: fitting different location parameters

[Hadassa Brunschwig]

Hi R-Help!

My question: I have lifetime/failure data of machines with different
stress levels and i think an weibull/extreme value distribution would
fit this data. So I did:

model1      <- survreg(Surv(lfailure)~stress,data=steel,dist="extreme")

(where lfailure=log(failure))

Now I would like to do a likelihood ratio test to test the hypothesis 

H0: location parameters of the extreme value distribution are equal
for each stress level.

So in order to perform the likelihood ratio test I need the likelood
of the model under

HA: location parameters are not equal (i.e. each stress level has its
slope and intercept).

How can I do this? 

Thanks for any help!

Hadassa