[R] manual recreation of varConstPower using new fixed effects variables in nlme

[JJ]

Ah, I think Ive found a solution.  A variance 
function of the form:

(d1 + (covariant)^d2)^2 + U,

can be made by altering the line in varWeights.varComb
to read:

apply(as.data.frame(lapply(object, varWeights)), 1,
sum)

Then the function varComb can be used as in:

varComb(varPower(form = ~cov1|g1,value=list(...)),
varConstPower(form = ~g2|g2, fixed=
list(power=(c(...)))))

That seems to work just fine.  John