hello all
I am using the R package Zelig for some tobit  regression with robust
standard errors.
I have got R version 2.9.2 (2009-08-24)
and Zelig Version: 3.4-5
when i do demo(robust)

It ends like this way

data(coalition)

> # Fit the model with robust standard error
> user.prompt()

Press <return> to continue:

> z.out3 <- zelig(Surv(duration, ciep12) ~ polar + numst2 +      crisis,
model = "weibull", data = coalition,   cluster = "invest", robust = TRUE)
*It is giving the following error

*Error in rowsum.default(resid(fit, "dfbeta"), cluster) :
  'x' must be numeric

Please help where it is going wrong
Thanks and Regards
Sayan Dasgupta

	[[alternative HTML version deleted]]


