Hello all,
I am trying to get the variance-covariance (VCOV) matrix of the
parameter estimates produced from the nlminb minimizing function, using
vcov.nlminb, but it seems to have been expunged from the MASS library.
I also tried using the vcov function after minimizing the function with
the nlm function and that produced the following error:

Error in UseMethod("vcov") : 
  no applicable method for 'vcov' applied to an object of class "list"

The hessian from nlm is also producing NaNs, although the estimates
seems to be right, so I can't get the VCOV that way either.  Any
potential solutions on this would be welcome.

Thanks,
Brian
Essentia Institute of Rural Health
Duluth, MN
55805


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