Hi Robert
You can try gnls() in the nlme package or if that is not suitable, try
to
follow the example in the nls() help page for weighted regression that has
an example of weighted regression from MASS.
from the nls help page:
## weighted nonlinear regression
Treated -
This question has been asked before on the list, but I'm not sure if the
answer were posted. Basically, the trick is to write the formula a bit
differently in nls() so that it does weighted least squares. nls() tries to
minimize the sum of squared differences between the two sides of ~. If you
