Lucy:
Why are you interested in robust standard errors from lme? Typically,
robust standard errors are sought when there is model misspecification
due to ignoring some covariance among units with a group.
But, a mixed model is designed to directly account for covariances among
units within a group such that the standard errors more adequately
represent the true sampling variance of the parameters.
So, the lme standard errors are robust in a sense that they are
presumably correct if you have your model correctly specified.
It would do better service to explain your issue a little more to get
better help.
Harold
> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Lucy Radford
> Sent: Tuesday, August 07, 2007 8:17 AM
> To: r-help at stat.math.ethz.ch
> Subject: [R] Robust Standard Errors for lme object
>
> Hi
>
> I have fitted a linear mixed model using the lme function but
> now wish to calculate robust standard errors for my model. I
> have been able to find several functions which calculate
> robust s.e for lm objects but have not been able to find a
> function which calcualtes robust s.e for lme objects. Would
> anyone know of a function that will allow me to do this.
>
> Many Thanks
>
> Lucy
>
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