[R] tobit regression model

[Jen]

Hi,
I'm trying to fit a tobit regression model to some data. When fitting the
exact same data in Stata, I have no problems at all, however R won't
converge. Its not a maxiters thing, since I've tried increasing this
already. I need to be able to fit the model in R since there are users of
the code that don't have a Stata license.

The code is:

require(AER)
left = 3.218476
x = c(0,6,12,18)
y = c(10.065819,7.803843,5.164786,3.218476)
mod<-tobit(y~x, left = left, right = Inf)

This gives back the following warning:
Warning in survreg.fit(X, Y, weights, offset, init = init, controlvals =
control,  :
  Ran out of iterations and did not converge

Has anyone come across this problem before or know a way to fix the problem?
Thanks in advance,
Jennifer

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