R nls results different from those of Excel ??
I use Excel regularly, and do not consider this a "slam"... it is a fact. I am aware of Solver, but the query was about trend lines generated by Excel. In general it is possible to do arbitrarily complex computations with a four function calculator, but we don't describe that as something the calculator does. Setting up a Solver sheet to obtain trend coefficients is not a typical way to obtain them in Excel... that would be the user's doing, not Excel's.
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Hans W Borchers <hwborchers at googlemail.com> wrote:
Jeff Newmiller <jdnewmil <at> dcn.davis.ca.us> writes:
Excel definitely does not use nonlinear least squares fitting for
power
curve fitting. It uses linear LS fitting of the logs of x and y.
There
should be no surprise in the OP's observation.
May I be allowed to say that the general comments on MS Excel may be alright, in this special case they are not. The Excel Solver -- which is made by an external company, not MS -- has a good reputation for being fast and accurate. And it indeed solves least-squares and nonlinear problems better than some of the solvers available in R. There is a professional version of this solver, not available from Microsoft, that could be called excellent. We, and this includes me, should not be too arrogant towards the outside, non-R world, the 'barbarians' as the ancient Greeks called it. Hans Werner
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