[Rd] evaluating variance functions in nlme
nikko at hailmail.net
Tue Jul 26 21:56:41 CEST 2005
I guess this is a final plea, and maybe this should go to R-help but
I am writing a set of functions for calibration and prediction, and to
errors and intervals I need the variance function to be evaluated at new
So for instance
Now using fit or fit2 I would like to get the variance function
evaluated at new points.
I have played with getCovariateFormula, and looked at Initialize.gnls,
but it is not clear to me how to evaluate the form component, especially
in the case of fit
above where form=~fitted(.), in any safe way.
I can grep for "fitted" in the formula eg.
and try to calculate predicted values from the model for the new points
but how to substitute back in the new terms?
I don't need this problem solved on a platter, I just need to unedrstand
because my stabs are failing.
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